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Finding a professor beforehand
I want to know your opinion about the following situation.
Having read all recommendations on how to apply to graduate school abroad, how to choose the professor to work with, I found a really interesting suggestion of someone. The person was describing the similar process applying to graduate school and in parallel he was looking for someone to work with in the same university, a bit early but if know what do you want to do, why not to do it. Having found a good candidate to work with, the person offered to work together for from few weeks to few months.
This person was lucky, he made a really good choice, they decided to proceed working together towards a masters degree and application to the university was a useless formality.
One minor point though, it was a quite expensive, to buy a fly ticket, rent a room etc.
What is your opinion about this form of finding a professor, do you have more examples like this?

Contacting potential supervisors before applying for Graduate School is a must. If you can't afford or haven't got time to travel, then perhaps try arranging a Skype meeting with them.

Whether it's a must depends on the sort of department and how they run admissions.  For example, in my department students are admitted by a committee, and I wouldn't want to try to pull strings to get someone admitted based on a Skype call or personal meeting if their application didn't look compelling to the committee (if I even could, which is doubtful).  And a large fraction of the applicants are rejected anyway, so it wouldn't be efficient to have the in-person discussions before the admissions decision.

Fair enough perhaps it's not a must in all fields but I don't see how it could hurt.

I didn't mean to imply it would secure a place either, just that it could help you decide if that academic is someone you'd be interested in working with

@LisaG: You must meet with an advisor before joining the group. It's not necessarily a must to do so before applying! (Particularly in the case Anonymous Mathematician describes—which also applies in my field.)

Well, if you want to find a good professor to work with, you could search for the available professors in a certain university (online, in their website).
After having all the names, you could "stalk" them online, find some of their papers, etc. Most of them (if not all) will have a webpage in which they post lots of information about themselves, such as, their papers, students they worked with, even their hobbies. You'll probably delete quite a few names that way.
You'll still have some professors names not crossed out. You can then try to e-mail the students they worked with and ask them what's their evaluation of said professor.
Not sure if this is what you're looking for, sorry if it's not.

thank you for the answer, according to my experience, the best way to understand whether you are capable to work with professor or not is actually to get to know him personally, talk to him, maybe start to work with him, the second good option, is to take courses he teaches, within three or four lectures you will be sure. By asking students I never received a negative evaluation, however half of them were unhappy with professor, which I learned afterward occasionally. Personal webpages might be very misleading.

I agree with your comment user10756. However, I still feel it's a good way to cross out some names. Also, I understood from your post that you wanted non expensives ways. Attending a few lectures abroad would be quite expensive, imho. You could try to search for online lectures. In comes down to this: If don't want to spend any money, that is, you don't want to travell aboard to have a meeting with a professor, than your only chance of getting to know, not fully know, but having some clue, of/your professor, than it is by searching him online, or asking people who know him.


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I regret my choice of grad school, is it possible/common to accept an offer I turned down a year ago?
I got accepted to three universities when I applied for grad school last year. There were two I was debating between and I chose one. Well, that was a HUGE mistake. The location is bad which I knew. I thought I would be able to handle that, but it's turning out that I can't...at all. The location is super depressing. There's nothing to do anywhere. Outside of my house there's always junkies hanging out shooting up. There was a meth lab around the corner that burned down. There is absolutely nothing to do, and the location is very far away from family. I couldn't see my family for some holidays which was very sad.
The location here is miserable, I honestly don't think I can handle another 5 years here.
I turned down another PhD offer, thinking I could handle this location. Well...I can't. The department here is ranked much higher than the other department. There's someone here I wanted to work with. But I don't even care about any of that if walking outside makes me miserable.
I don't care if none of my credits transfer. I don't care if I have to start over. I just can't handle this location. The only thing I don't want to go through again is applying and waiting to hear back, asking for letters of rec, etc.
I emailed the other department (who DID accept me last year, even with a fellowship) if there's anyway to transfer that doesn't require applying again.
Is this common? Is this possible? Or am I just stuck here or stuck reapplying?

I think you'll have to wait and see what they say.  But even if you have to reapply - if you were a good candidate before, and you've been reasonably successful in between, you will most likely be a good candidate again.

This is why you always need to do a campus visit -- and stay overnight with a current grad student in their housing.... :-(

If you emailed the other department to ask there, I don't understand the point of asking your question here.  They're the only ones that can give you a definitive answer (though it is very uncommon as RoboKaren says).

This is why universities should not be chosen solely on the basis of the ranking: daily life is important for serenity.

Why do you have to live in that particular house? You could move to a different part of town.

I've lived in some pretty terrible places (including with the meth labs burning down near by), but even in that particular place there were some less terrible areas that were still affordable. You might consider if there are less extreme alternatives to living in a nicer area, talk with people in your program about local clubs and groups that might have activities you had not heard about, etc. I'm not saying that moving won't be right for you - but I also know that moving across the country doesn't always make your problems go away. It's at least worth trying while you look at other options.

There's almost a 100% certainty that you'll have to apply again. Graduate programs get a fixed number of admission slots (or fellowships to support those admits) each year. Your position was likely given away to someone or returned to the graduate school when you told them you weren't going.
As Nate Eldridge notes, you were a good candidate last year and you'll be a good candidate this year. There's a slight stain on your record regarding whether or not it was a personality conflict or something else that is causing you to abandon the other school.
If you have a good relationship with your current advisor, then s/he can address that in their letter of recommendation. Or you can ask your undergraduate advisors to note the reason why you're leaving the university.  The faculty on the admissions committee will be curious why you're leaving a more highly ranked program and admissions committees are risk-adverse, so you do need to address this somehow.

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Does copying facts from Wikipedia, with attribution, constitute plagiarism?
I had an assignment where I had to create a web-based advertisement for a Computer that was created in the 1970 era or earlier. In my advertisement, I copied facts from Wikipedia such as "Output consisted of a row of lights", "The machine was programmed in pure machine code using an array of buttons and switches.", "The 8-bit machine offered 256 bytes of memory, implemented on Intel's type 1404 silicon gate MOS shift registers." And I cited my sources at the bottom of the site. Does this constitute plagiarism since I have copied facts and not opinions, and cited my sources?
Thank you!

Why do you have to 'steal' those phrases?  There are many ways to convey that info.

Did you quote the phrases as you have here?

Your question doesn't seem specific to Wikipedia, but since you did use Wikipedia, it's worth pointing out: Did you properly cite the specific revision of the Wikipedia articles you cited? On every Wikipedia article, in the lefthand navigation bar, you'll find a link called "cite this page". This will give you easy access to a permanent link to that revision. Important to use, especially in a case like this, where it might be difficult to find the exact phrase you copied.

I'll assume the quotation marks were used in the advertisement.  Since you represented the text as coming from the reference, and provided the reference, it's not plagiarism.
That doesn't mean it's necessarily okay.
If the purpose of the assignment was to practice writing advertisement text, then you didn't do that and didn't complete the assignment.
If the purpose of the assignment was to practice graphical design, you might have done that, and the text might be okay.
In any case, ask your instructor what they want you to do before you submit your assignment.

+1 I feel we should have some canonical answers for plagiarism related questions, because the answer always seems to be "it's not plagiarism if you cite your sources correctly, but that doesn't mean that you won't fail / get 0 points.".

Plagiarism is not a "legal construct."  That is copyright infringement.

@AnonymousPhysicist  Copyright is ALSO a "legal construct". More formal, fortunately, but Plagiarism is as well.

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How can I write a research paper as 'original contribution'?
I have been told by the editor that the paper does not have original contribution to literature development.
However the framework is derived from the past literature with complete citations and acknowledgements. There is no plagiarism.
The context of study, place and framework is new.
I am unable to understand how to write the literature convincingly that it's a original contribution.
P.S.: I don't know anyone who would like to see the paper and provide suggestions for improvement.

My impression is that the editor is saying your paper doesn't advance sufficiently beyond the previously existing literature, but that your understanding of the editor's message is that you're somehow mishandling the treatment of existing literature. The fact that you're not mishandling it (that you're providing complete citations, etc.) refutes what you think the editor meant, but not what I think the editor meant.

PS: I don't know anyone who would like to see the paper and provide suggestions for improvement.

I'm afriad this is your biggest problem, and somewhat of a red flag. Are you an undergraduate or graduate student? Do you have a research advisor who is active in your field? Why is there no one who can read it? It sounds like either:

This is independent work that you are doing as a student without a mentor, or
You are working in a very isolated program without feedback from professors and mentors.

Either way, this is a bad sign. If there is no one to read the paper and provide suggestions, it is very unlikely that you will be able publish successfully. It is just very difficult to produce a publication-worthy paper without mentorship, and more generally, feedback on what you are doing.

I have been told by the editor that the paper does not have original contribution to literature development.

This sounds to me like a generic message that just avoids saying exactly what is wrong with your paper. For example, perhaps the editor desk-rejected your paper because they didn't feel it met the standard of quality for a good academic contribution. It is hard for us to tell without further context. Keep in mind that what counts as an "original contribution" does vary a lot by subfield, but your problem might be something else entirely.

However the framework is derived from the past literature with complete citations and acknowledgements. There is no plagiarism.

This is necessary but not sufficient for your paper to be an original contribution.

The context of study, place and framework is new.

It sounds like it is new in your judgment, but not in the editor's judgment.

I am unable to understand how to write the literature convincingly that it's a original contribution.

It's not just writing the literature (related work), but structuring the entire paper, and perhaps doing the research itself. Ultimately, you will not be able to proceed without feedback from an established professor who can give you good advice.

I tried to connect with some professors in the field requesting their feedback on the paper. But it seems people are just very busy or uninterested in providing feedback or time.

Very likely this has been done before, either exactly or nearly exactly, and you simply are unaware of it.
If you’re keen to argue your point, start by politely asking the editor if she or he could provide you with citation details of works duplicated by your manuscript as you are obviously interested in the topic.

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Applying to several faculty positions within the same institution
The following question is not a general question about applying to many academic positions at different institutions, but rather about applying to several positions within the same institution (regardless of applying to multiple other institutions as well).
Starting questions are, as follows. What are the potential effects, following such strategy? Mostly negative, mostly positive, or neutral? A situation often occurs, such that an institution advertises several positions that I believe I would fit, however, among those, only one (usually) is the best fit (my preference), but others are also suitable (decent fit).
Therefore, my main question is twofold: 1) is it a good strategy to apply to all suitable positions within an institution; 2) if Yes, should I mention my preference, for example, in an application letter (if No, I assume that the optimal choice is to apply to the position with the best fit)?

How are these positions different?  Are they in different departments?  Or different sub-disciplines within the same department?  Are they for positions of different ranks?

@Kimball: It varies from one institution to another - mostly, those positions are within the same department (usually, of a business school), but within different groups. Ranks vary to a larger extent: from lecturer (visiting faculty) to assistant professor (non-tenure-track or tenure-track - I don't care much about that aspect at this point).

@Kimball: I meant "might be within different groups", not necessarily.

I advise against applying to all open positions at once. Not only are you likely not to match the criteria for many of them, but you are also not interested in accepting the majority. By doing so, you just add to the workload of the hiring committee. Furthermore, you decrease in a way the value of your applications, as you should be striving to emphasize how you are the best fit for that particular position and that gets very hard when trying to apply to many different positions. You'll likely end up with mediocre applications everywhere or worse with the same application everywhere.
Typically, there is one position (as you say) which you would like to get and are probably best suited for (depending on your qualifications). So I suggest you narrow down the open positions to at most 2-3 where you would most enjoy working, if you insist on having a safe option, and try to write strong applications for all of them.
Finally, I don't see how a "preference statement" would help you. If you get your desired position, then it is not due to your preference, but because you had a stronger application than other applicants. If you, however, fail your best option, other options might see it as a negative thing, if you stated that you'd prefer to work at some other position and only failing there, apply to them. So, the idea is to apply everywhere with the same zeal. That's also why you have to narrow down your options, so you can accept any outcome, if needed. If you are not comfortable with that, it means that the options aside your primary are not attractive to you and I would refrain from applying to them (assuming of course you are not in a position that you have to accept any job). In the case you get accepted on more than one position, you are of course free to choose.

I appreciate your insightful answer (+1, acceptance is TBD). Just to clarify: I specifically emphasized all suitable positions, which in practice results in no more than 2-3 (and even that is for very few institutions).

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Postdoctoral job search: mixed applications
As I'm currently pursuing an academic job search (in parallel to the industry one), which includes potential postdoctoral positions, I would appreciate some clarifications on the following aspect.
Mixed applications. At some institutions/departments (usually, large), I see multiple positions that I think I would fit well. Perhaps, one is the best, but, considering the tight competition, I consider it as a luxury to apply to a single position per institution. Important: unlike that question, this particular one is concerned with a situation, where multiple positions, which I consider, constitute a mixture of postdoctoral and staff [with some teaching- and/or research-related support component] positions.
Question: 1) assuming that the other positions are also quite interesting (and they are), is it a good idea to apply to all of them or apply to several in groups (of one or more) of decreasing excitement or stick to the most interesting or valuable? 2) do applications for teaching- or research-related staff positions jeopardize the ones for postdoctoral positions (or junior faculty ones, for that matter)?
Note: My field is Information Systems, a discipline, which can be considered as a sub-domain of Management Science, which, in turn, is a social sciences discipline.
UPDATE (clarification). This question is not an exact duplicate of the suggested question, even though they are very close. The question you're referring to, covers only a subset of my question's scenarios. For example, it doesn't cover one of my real cases, where there are several postdoc positions within the same department (lab) - no junior faculty positions there.

Somehow, the note in your question reminded me of this.

@TheDarkSide: Ha-ha :-). But, on a more serious note, the arrow could very well be reversed, if the key word would be complexity, instead of purity.

@AleksandrBlekh Are these positions at the institution with the same people, or just in the same institute/department?

@Fomite: Mostly, the same school/department; intersections are unlikely, though not impossible.

possible duplicate of Should I simultaneously apply for multiple jobs in different ranks at the same university?

@Mangara: Thank you very much for the link. Please see my update.

I rarely find people applying to one job and moving on. Doing so involves a lot of risks. In applying to the one job you believe is best, and getting rejected, you keep delaying the hire date of the job you may get. In waiting for a response from your perfect job,the alternative positions may be filled or closed due to lack of appropriate candidates. Point is, the norm is for people to apply to multiple positions, across universities or departments, or even within the same department or doctoral college.
One person in their search applied for two positions within the same department, both of which he was well suited for; both positions will from here on out be referred to as positions A & B, respectively. The person preferred job A, but for reasons like the ones mentioned above, he applied to both. He was contacted for both positions and was deemed fit for both positions. The supervisors then realized that they had the same candidate; enter inter-departmental politics. Eventually, the supervisor of position A yielded and the person was assigned to position B. The point here being, there exists a possibility that it is no longer your choice which position you take once you apply to multiple positions in the same department/university, less so within the same field.
Also, if you receive an offer for a position less preferred and you accept, do not renege if you receive one for a position you prefer more. Aside from the ethical and moral issues, the person you just harmed will be your colleague in your field for many years to come; i.e. this may also harm you professionally.
As for the last part of your question, you'll find plenty of examples of people that occupy any number of roles as a PhD, lecturer, researcher or post-doc. People also tend to move fluidly between these positions. It's also worth mentioning that it is irregular for a post-doc or researcher to not lecture. This is as the post-doc/researcher requires students to fulfill certain portions of their research. To do so, the post-doc holds a lecture, at least, the moment they begin their work in order to attract students that are interested in his/her work while ensuring that they would research their part of the work while having the necessary foundation in place. This covers a post-doc that wants to lecture.
In the case of a lecturer that wants to apply for a post-doc position, you're directly in contact with the supervisors and have an insider's insight into their work. If anything, you could create your own post-doc position by attaining approval for supervision from a professor, and then securing your own funding from a funding institution (DARPA, etc.). In short, as far as I've seen, no, it doesn't harm your chances, but rather improves them.
Sorry for the long post. Hope it helps.

Excellent answer - greatly appreciated (+1; will likely accept, if no better answers will appear). Your points are very much in line with my own thoughts.

I imagine your application is composed by a cover letter as well.
I think it is appropriate that you explain in 1-2 lines that you are applying to another position within the same institute and explain the reason, as you have done in your question. It seems neither strange nor inappropriate to me.


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To what extent do grades matter when applying to graduate school in mathematics?
I understand that applying to competitive pure math PhD programs in mathematics in the US/UK definitely requires good grades (A or above) in most math courses - but I'm wondering how bad is it if I have one or two B's or C's? Are there other factors that can help me shadow my not-so-good grades while applying? (of course, only in 1 or 2 courses).
In particular, the course that didn't go so well for me this fall is a second course in Linear Algebra, and I ask this since I am a little worried about the situation.

A single bad grade is unlikely to matter much. A history of bad grades is worrisome. Your application to a doctoral program needs to show that you have high likelihood of success in (math) research. This implies that you can demonstrate insight into areas of math that you want to specialize in.
But insight in mathematics isn't uniform over sub-fields and mathematicians understand that (I hope, anyway).
In the US, there are many things taken into account besides GPA and even individual grades. So, you are right to be "a little worried", but not to panic.
But, for some people, even a poor academic history (not like yours, I think) can be overcome by other factors.
But you might want to be ready to answer a question or two about why you got lower grades in a few courses. Lack of insight is only one possibility. Taking too many courses in a term is sometimes a factor.

The issue is most often not what happened a few years ago, but what has happened most recently. That is, what is the shape of the arc of your grades?
Many people take some semesters to get in sync with math programs, and early troubles are not surprising.
Grades of relatively recent, relatively basic courses matter quite a bit, though still not perhaps completely critical. But/and people will start to wonder (relevant to the typical U.S. math grad program set-ups) how you'd fare in grad-level courses if you've had recent difficulties in their prerequisites. Indeed, I'd think some self-examination about that question might be warranted, insofar as even most "advanced" undergrad math is very, very standard, not "specialized", and really pretty necessary no matter what kind of specialization one might eventually take up.

I'm only a sophomore, and this is my first theoretical math course - so I think this early trouble shouldn't be too much to worry about then? I have most of my undergrad left, and I'm confident I'll take care of the shape of the arc of my grades.

If you're just a sophomore now, you have a few years to figure out not only math itself, but how the system there works, so that you can succeed in it. So, no, not so critical to be out-of-sync when you're a sophomore...


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Is it common practice to have a separate "Further Discussion" after the conclusion in an academic article?
I received reviews of my manuscript for IEEE Transactions.
One question from a reviewer, about a common misconception regarding the technology, is interesting but is not relevant anywhere else in the paper. So, my supervisor suggested that I add a new section after the conclusions titled "Further Discussion."
I was just wondering if it is common practice to have such a section.

Virtually all papers I've seen end with the conclusions section (otherwise, it wouldn't be the conclusions!).
The best way to incorporate such changes would be to include it at the end of the current discussion section. Perhaps you can subtitle it "A brief note on X," where X is the topic of the comment. Alternatively, you could include it as an appendix if it requires a more extensive and extended discussion.


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I submitted a paper to a journal one week ago. What does "Awaiting ME Processing" mean?
The status from the very 1st day is "Awaiting ME Processing". Can someone tell me what does it mean?

The acronym ME most likely stands for "Managing Editor" or "Manuscript Editor", and so the message says that the paper is awaiting processing by this person.  As shown in this question on the process for journals, that initial "processing" step usually involves an initial assessment by that initial editor, and if it passes that hurdle it will then be sent out for peer review by referees.


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How to write a technical paper of a not so significant idea?
I am a PhD researcher in my first year. For the first 3 months all my supervisor made me do was read related papers on IEEE, so a LOT of literature review.
Recently in trying to recreate the result of another paper I was reading, I wrote some code on segmentation that appears to work really well and has got my supervisor's attention and interest. He thinks this may lead to a publication.
He asked me to write a technical report on it. So I wrote a simple report in MS Word which included a brief explanation of the method with graphs and result images but he said this is not what he wanted. What he expects from me is a IEEE style report/paper, including introduction, algorithm/method explanation, mathematical representation, experiments, future work etc.
The problem is that I believe he thinks too highly of my code, its just a for loop applied at different settings. That is all..
What is the mathematical representation of a for loop? How do I make it look more professional? As I know my reports are those of an undergrad standard.

It's important to remember that nothing in research is very significant, right up until the point that it becomes significant. It's ok not to win a Nobel Prize with every paper - indeed, if it only moves human knowledge forward by a grain of sand or adds a tiny amount of support to an existing study, that's ok. Treat it like it's just exactly what it is: of unknowable significance or importance to anyone else. Write it up like a full "holy moly stop the science presses" amazing discovery. It turns out those great papers tend to be written about the same as the insignificant ones.

all great as well as bad discoveries in computer science can be described as "a for loop applied at different settings"

I wrote a simple report in MS Word You should really start using Latex. Your career will only benefit. A lot!

Quite possibly, your supervisor is encouraging you to write early, to learn how to write, and to get into the habit of writing your results down.
You would gain a lot by watching this youtube video by Haskell inventor Simon Peyton Jones on How to write a great research paper. Part of his message is that you can do the research while you are writing, meaning that many ideas will come to you as you are writing things down.
You ask how to write a paper. Didn't you just read a whole bunch? Pick one that you found easy to follow and inspiring. Model your paper on its structure and style.
Regarding the actual work. A formal model of a for-loop has already been done, so I suspect that this is not the right level of abstraction to consider. What is the data to which your for loop applied? What did it mean? What did the parameters mean? How are the results of your code interpreted? Were some better than others? On what scale?
Part of science is learning to ask and answer the right questions.

+1 for having deleted the comment about using LaTeX instead of Word.

@AvengerDr: I couldn't help myself, initially. I suspect that earned my a downvote.

Thank you for that answer and the video. I actually did read the comment about Latex before you edited it out. Can you please tell me why you removed the part about using Latex and avoiding word? And why is that an unpopular opinion (since it got you a downvote). As I was told to get a journal submitted I must submit my latex code.

Some people think that Word is perfectly suitable for writing papers. Indeed, many people do actually write their papers in word. It is a matter of personal opinion, so not really totally appropriate for a site like this.

@Dave: Your assertion that LaTeX is better than word for science students is a professional opinion, not a personal opinion (that would be, e.g., that you think cowboy hats are fashionable).  Surely rendering professional opinions is a big part of what answering questions on this site is all about.  Assuming that you still stand by your statement about LaTeX (I would and do make that statement for math students without batting an eye), I think it would be a service to the OP and others to include it.

(Maybe you could write it in a slightly "nicer" -- or really, more transparently explanatory -- way.)

From the wording of your question, it looks like what you wrote can be summarized as "I wrote this code and obtained these results". Even if your code and results are correct (I assume they are, if they got your prof's attention), this is not a publishable paper. The reason is that "I wrote this code and obtained these results" is something that you can say of any piece of code that actually works, no matter how trivial or mundane. What your prof is expecting you to write is a paper that says "I wrote this code and obtained these results, and this is interesting to you, dear reader,  because...". There are a bunch of reasons why your code is interesting: it might run faster than standard code for certain cases; it opens up a different way of attacking a certain problem; it shows that a certain cases have some properties that set them apart from their complement class; and so on.
If you had decided to go into industry after getting your BSc, you would be paid to write code that works, period. In grad school, on the other hand, whether your code actually works is to some extent secondary (cf. Knuth's quote "Beware of this code: I've proven it correct, but I haven't run it yet"). What matters is whether your code teaches your peers (grad students, postdocs, profs) something new about your (sub)field.


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The utility of graduate math study for theoretical physics
This is question that should primarily be answered by theoretical physicists, as mathematicians always are going to want to say to take more math.
I am going into my third year of undergraduate study major in math and physics and I hope to eventually end up in a good theoretical physics PhD (probably cosmology or particle physics). I have the ability to add a year at my current institution and do a masters in math, and I am trying to figure out if pure math at a graduate level is interesting/useful for serious theoretical physics.
Some classes I would be interested in taking as part of the degree would be (all grad level) Functional Analysis, Complex Analysis, Lie Algebra, Differential Topology, Riemannian Geometry, Theory of ODEs, Theory of PDEs, Operator Algebras, Real Analysis, Topology, Algebra (a lot of these classes are two semester sequences).
I am interested in hearing how useful people think having such a formal mathematical education would be to doing the physics. I am primarily interested in very foundational physics, and I am concerned that the brief treatment the math is given in physics books will prevent me from having a full understanding of the math at play in fields such as QFT and some the more out-there cosmology. I of course understand one can self-study some of these topics, but it seems fairly clear one would get a deeper appreciation by actually taking the courses in a proper academic setting.

Differential topology and Riemannian geometry would both be useful for cosmology. As a cosmology PhD student myself, I wish I knew more pure maths so I could understand/ appreciate physics a bit better but it's not actually necessary for doing cosmology. Basic algebra and calculus is sufficient for 98% of what I do.

I might attempt an actual answer later, but my main point would be that it really depends on the nature of your research - probably just as much as the subject matter itself. Do you think it'll be on the formal end (say of high energy theory), more numerical, or otherwise?

@Anyon I'm still an undergrad so it's hard to be certain, but what I think I would be most interested in and good at would be the formal/pure theory stuff. I'm going to start working with a theoretical cosmologist that does BBN and dark energy research over the next year so I'll get a better idea then, but right now I'm doing research in computational accelerator physics, and it is certainly not what I'm interested in.

@astronat Could you elaborate on how pure math is used/taught in your study. I've never understand how physicists go around using math like differential geometry, functional analysis, various algebras, etc. without so much as taking an analysis class. Do you work with anyone with more formal math training, and do you think they have a different perspective or an advantage in any way?

@Keefer I was taught differential geometry as part of the general relativity course I did in the 3rd year of my undergrad. Three of my fellow PhD students did maths undergraduate degrees and if they hadn't told me I don't think I would be able to tell. As Anyon says, it really depends on your research direction, and if you need to understand some bit of maths to make progress in your research, you'll probably just learn it on the fly.

I could do it by adding only a year and it seems impossible to get that kind of pure math exposure without some kind of formal graduate study in Math. I agree it's a bit odd though, that's why I'm wondering what think about its usefulness.

@astronat Yeah, I've read Geometry and Spacetime by Carroll and while I think he does a great job introducing the math, and I think you could very well understand it enough for most applications through that book and books like it, I don't think his treatment gives the full depth necessary if you were actually interested in developing theories reliant on that math. E.g. his treatment of directional derivatives <-> vectors and gradients <-> dual vectors is a little too fast/superficial to give a complete understanding. I would prefer having a more rigorous basis.

@keefer then you have your answer.

You need to distinguish between a few different styles of theoretical physics, which differ dramatically in their math requirements.

Particle phenomenology and theoretical cosmology. These are the people who use math to make predictions about our universe. They study things like dark matter, inflation, (low-energy) supersymmetry, baryogenesis, grand unification, etc., and often talk directly with experimentalists. (hep-ph/astro-ph on ArXiv)
"Formal" theory. These are the people who play around with neat theoretical toys like supergravity, AdS/CFT, strings, twistors, etc. without worrying much about whether they have anything to do with our particular universe. (hep-th/gr-qc on ArXiv)
Mathematical physics. These are the people who try to put physics on a firm mathematical foundation. The Navier-Stokes and Yang-Mills Millenium prize problems fall under this category. Many professors who work on this have stuff have joint appointments in the math department. This camp is much smaller than either (1) or (2). (math-ph on ArXiv)

Lumping them all into "very foundational physics [...] such as QFT" and "formal/pure theory stuff" makes it sounds like you haven't learned enough physics to know what you want yet. All of these groups will use QFT, in very different ways. You should talk with professors and grad students who do each of these things and look at papers on the ArXiv to see what catches your interest.
If you want to do (1), you'll probably need to pick up differential geometry, group/representation theory, complex analysis, Lie groups and Lie algebras, and the very basics of algebraic topology (i.e. what a homotopy group is). The most efficient way to do this is to read math books written by physicists for physicists, which are listed here. If you take pure math courses on these things, as I have, you'll find that what the mathematicians care about is very far from what physicists care about! About 80% of the material in any given course will be irrelevant.
If you want to do (2) it will depend on exactly what you're doing, but it wouldn't hurt to get full year-long courses on differential geometry, algebraic topology, and algebra under your belt, in addition to the material in (1). Most PhD students have done this or done the equivalent by self study. While you'll rarely see math-style proofs in such papers, they will use the language of pure math, and the benefit of the courses will be acclimating yourself to this language. If you want to do (1) this background can still be useful because it makes papers from (2) much more accessible.
If you want to do (3) you'll basically be a mathematician, so you should take everything you mentioned and ideally enjoy it very much. You'll need more advanced graduate courses too, though which ones will depend on exactly what you're doing.
If you have more questions, feel free to drop by the Physics.SE chat room where we have people in all three camps!

I sometimes refer to research or type (3) as "stuff that mathematicians think is physics."


text:
Returning to university
I graduated from an undergraduate maths course from a prestigious university. However, I was rejected from attending it's master's program due to poor showing in the final exams. I'd like to study at said university again sometime within the next few years, applying for the same course. In applying though, I will almost definitely have to use the same final exam results. What can I do to show that I have improved, if I indeed have? I am not currently enrolled in any graduate level program.

In the next 2 years. :)

Yes. I've looked at the admissions process and it was mentioned that there will be no interviews. So I'm guessing that there might not be an entrance exam. I've asked about it, but they have yet to reply. I plan to do some self-studying the next two years in preparation for graduate level maths.

At many schools, particularly those rated highly, the most important parts of your PhD application are your letters of recommendation.  What many applicants don't grasp is that a PhD program is so different from undergrad that past performance in the latter is only a poor indicator of future performance in the former.  For most students, the hard part of a PhD is doing original research.  So, as an applicant, you must convince the committee that you will excel at doing research.
One way to make your case is to have already successfully done research (or some "research-like" project).  In the absence of this, you must somehow convince your letter writers that you will succeed in research (and then they convince the admissions committee).  Meet with your letter writers and ask them what they suggest.  You might even ask them if you could work on some research with them (prior to being admitted to the PhD program).

Have you considered directly contacting the admissions committee or a former teacher and asking for advice? They'll probably be wary of saying anything that sounds like "if you do x,y, and z, you'll be accepted", but even if they're unwilling to share specific advice they might be willing to tell you what other experience (beyond the exams) they consider during the admissions process. A bonus of contacting the admissions committee in a respectful and professional manner is that if you do indeed follow through on any recommendations they give you, you can mention this in you application as evidence of your commitment to improving.
You might also ask if you can retake the test--either officially (i.e. if they'll replace your old results with your new ones) or unofficially (i.e. your old results will still be the official ones, but at least you have some metric showing your improvement).
Another option is to talk with a professor in the department with whom you have rapport and ask them about how to frame your rejection in your application when you reapply. For example, is it considered good form in your field to discuss what led you to do poorly on the exams (whether this was some unrelated life experience, or a lack of preparation)?


text:
How to refer to a page number in a pdf?
Many times, the page number in pdf is different than the printed page number. How to make sure the other person doesn't get confused when we say "it's on Nth page".

See also http://academia.stackexchange.com/questions/1240/should-i-cite-a-journals-page-number-or-an-articles

Refrain from referring to the printed/PDF page number at all, and refer to something more concrete, like "in section X" or, of course, a particular figure number if you're referring to a figure.

If you're talking about the PDF of a paper published in an academic journal, then the answer is unambiguously: refer to the journal page numbers, i.e. the numbers at the bottom of each page. Those are the ones features in (almost all) citation styles.
Otherwise, if the document is a random PDF found on the web (not coming from a journal), just avoid referring to pages. If you absolutely must, refer to the page numbers printed on the paper, as it is the only thing that makes sense to someone who would print the document.

Thanks. How to refer to a particular paragraph (in informal discussion)?

Give its position in the section (“in the third paragraph of section II.C”). If that's too hard, quote its beginning (“in the paragraph starting with ‘We report here work performed at the Mars Permanent Bases in 2034’, the authors …”)

Some journals number each individual paragraph, but I've never seen a citation mentioning a particular paragraph.  Most papers seem to not refer to any page or specific figure at all when citing results.  Of course one may still wish to do so in other contexts.

"See the discussion after Theorem 3."

In informal communication like email I use a notation along the lines of "page X (PDF page Y)". By providing both numbers, it is easy for whoever is browsing the PDF to figure out if X or Y is referring to the internal page numbers or the PDF page, and then use whichever one they want to find the content.


text:
Standard for figure description in main text and its placement in a report/paper
I heard of this rule/recommendation (or may be its opposite) - Always let the figures come after they are described in the text.
What is the correct rule? What's the logic? Is it always followed?
What if (in a single column format) there are two smaller figures side-by-side and second figure's description comes later in the text?

The following applies:

Figures should appear at the first possible place after they are referenced in the text and thus also in the order they are referenceed in the text. (the physical placement of the figure follows typographical rules).
A figure may be placed before its reference if they are on the same page. Figures are normally place at the top of pages.
Figures must be ordered according to the order in which they are first referenced.
The same system also applies for tables. It is however, not necessary for figures and tables to be placed in the order they appear relative to each other, they are two independent series of inclusions and placement depends on typographiccal rules.

The logic is that the order figures are needed in the text also determines their location. Having such a rule makes the location predictable. Thse rules are followed by all journals typeset by professionals.
The case of the figures is dealt with as follows. If a figure has two panes, they would count as one figures but be labelled (a) and (b). thus one can reference figure Xa in one place and figure Xb in another. Combining panes into larger figures is a way to save space but most importantly to group plots that relate to each other in one place. ths is one way in which the order of figures according to the list above can be circumvented.
The important aspect is that figures should make sense and provide the reader with as much information as possible. Placement is done according to a logical and predicatable rule so that we all know what to expect.

I was told by an editor that (2) was not ok, an never had a requirement for the top of the page.

Are these fixed rules or just accepted practice - are exceptions ever granted at an authors request?

I've had it as a requirement by an editor at a journal (after mention in text). I guess the rational is that figures are catchy, if you see one, you will probably want to know why it is there and parse the text to find the reference in the text. Doing so, you might omit reading part of the paper.


text:
about referencing of exercises?
I am using different programming books for extracting problems to be applied to a group of students for practices and exams. I would like to know if its necessary to put from where I took the exercises. I always reference the material in my lectures, but in exams is this necessary?
Thanks

It may have a side-effect. If the students know that you usually take exam questions from X/Y/Z books then they will mug up them. This can happen even now in case someone tries to google the text of your exam problems.

I take those problems from the prescribed books for the course

@Layla I think you might under-estimate the power of Google. The students in these days rather spend time on Internet to find the sources of the exercises than trying to figure out the solutions of the problems. They seem to think it's more fun to search than working out the solutions themselves. I don't understand why. Just my observation.

To your specific question: I would not worry about referencing questions on an exam.  Although exams could end up on the Internet if a students posts them, I find it hard to believe that "fair use" does not cover using the questions for internal educational purposes, and referencing the questions is almost certainly not necessary.  That said, I am not a lawyer.
The bigger question might be

How does one come up with good test questions?

It used to be (and may still be) that fraternities kept a filing cabinet full of course exams used in a class from year to year, purportedly simply for study purposes, but also in the hope that professors would re-use questions from year to year and this would provide a huge advantage to those studying from the prior exams.  These days, it would be trivial to have a web page dedicated to scanned copies of old exams.  Therefore, I would advise against re-using too many questions on an exam, or at the very least modify old questions to make it difficult to simply re-apply the exact same methodology to solve.
Crafting good questions is always challenging, but some would argue that it is fun developing questions that test the students ability to problem-solve in a format that works on a timed exam.  Questions that have a single answer are easier to grade, but could limit the ability for a student to think outside the box, or to solve using alternate methods.  Depending on the subject, this isn't always possible, either.
I am of the opinion that the best tests have many different types of questions, so students can show their own strengths in different ways.  For programming tests, there might be a few questions asking students to describe what blocks of code do, others that ask the student to find syntax errors, others that ask for algorithm deficiencies, still others that ask the students to draft short snippets of code, and finally some questions that demonstrate that the student knows when to use certain constructs (e.g., when is a "do while" loop appropriate, and when is a "for" loop appropriate?  How could you turn the following "do while" loop into a "for" loop?).
As a bottom line answer to your question: I would not worry about referencing the questions on the exams, but if you are worried about students cheating by looking up the references for future exams, it is probably worth trying to obfuscate the questions themselves, or to at least change them enough that studying the questions directly from the references will not give an unfair advantage to the students that do find them.


text:
Prospective PhD contacts potential supervisor but receives no answer after 2-3 emails, what to do?
Say a prospective PhD has a high reply rate (90-95%) to first contact emails with potential superviors. He/She has a well thought out e-mail, but a particular professor (here: USA) that is in the top preferences does not reply after two to three e-mails that were sent within a time frame of three months. I also followed the instructions on the professor personal website in the section "prospective PhD students". The student has already contacted some of the advisor students and has received positive feedback about the professor.
Should the student just give up and move on? Should the student keep trying?
Aside from the obvious "I have too many incoming e-mails to answer" or "I am out in the field", what could create a no response behavior from the professor?
I have seen the simplistic answer "move on, bad advisor, doesn't have time, etc". But this seems a contradiction in this case. The PhD students like the professor and say he/she is personable and no e-mail response after a few well written emails.

What is the time windows for your 2-3 mails ? If this is 1 week or so you should wait that the backlog reaches one of the emails you sent. BTW, even if I know this is unfortunate, I don't answer to prospective students if I know I will not "take" them, because I receive too many emails from prospective students (I mean several each day while I am certainly not a "top preference", so imagine for famous profs). But if a student insists, I will probably end up answering after 2 or 3 weeks.

Some more background might be helpful here. Are you looking at applications in the US or overseas?

I am not sure if locations matters too much. I am specifically referring to a US scholar, the only that has not replied after a few e-mails sent over a 3 months period. Another person in the UK responded after the second e-mail. I know for a fact that the former person is highly sought after but I don't think it would be more sought after than many other people I emailed.

Was there a procedure set out on the department's website, for prospective PhD students? Did you follow it?

Yes I did! I also followed the instructions on the professor personal website in the section "prospective phd students". As a matter of fact I successfully implemented some of those strategies in contacting other profs.

What are "advisor students"? Other research fellows / assistants? I would frankly never have the balls to contact the professor in case directly. I always e-mailed everything (letters of recommendation etc.) to his secretary or research assistant! This always worked. Only the rude people wrote directly to the professor.

Write to or call their secretaries and ask politely. They'll know whether their boss is away, reads email at all and how they treat requests such as yours. Or, and that has happened to me, they walk over to them and solve the issue in minutes.

I am going to assume we're talking about a student who plans to apply to the PhD program that the faculty is affiliated with, but has not yet been admitted.  (You didn't say explicitly, but reading between the lines, that is my assumption.)
If that's the case then the student should not expect a response and should not read anything into the lack of a response from the faculty member.  Many faculty do not have time to respond personally to all enquiries from prospective applicants.
Please understand that some faculty receive dozens or hundreds of enquiries from prospective students.  For example, my understanding is that many Indian or Chinese students are under the mistaken impression that they should contact faculty, or think it will help their case for admission somehow (not true; but they don't know, or have been given bad advice, so they write).  Anyway, as a result, many faculty cannot possibly reply to all such contacts.  I've even seen a few faculty post a FAQ on their web page which explains why they cannot respond to such inquiries from prospective PhD students who are interested in applying.  In many cases, it is likely that few or none of those who contact the professor will be admitted, so professors may understandable decide that they cannot afford to to spend time responding to such contacts until after admission, in most cases.
To learn more about this, I can recommend some additional reading:

Advice for Prospective Research Students - a FAQ one professor posts, about how to contact professors
Writing to me - Advice from Female Science Professor (a pseudonymous professor/blogger) about how prospective grad students should write to her.
In general, anything from FSP is worth reading.  Here are some additional posts of her that are relevant, and that may help to understand the professor's mindset:

Mad Libs Gone Mad
You Can Lead a Horse to Water
What They Don't Tell You in the Non-Existent Training for this Job

If I have misunderstood the status of this student:
If the student has already been admitted into the PhD program where the faculty is affiliated with, but has not yet accepted the offer of admission, the lack of response probably indicates lack of interest or lack of time on the part of the faculty member.  In this case, my advice would be to move on.  As far as I can tell, though, this response would be a bit unusual: if the student has been admitted, it typically means that at least some quorum of faculty think highly of the student.
Finally, if the student is current enrolled in the faculty's PhD program, the student should go visit the faculty member in person.  Faculty have office hours; go use them.

To try to make a clear point: there is a range of opinions about how to respond to "cold calls" from people I don't know, etc. I myself find it easy to make a one-or-two-sentence response politely thanking an inquirer for their interest, but (if so...) that I "have no open positions in my group at this time" or whatever is suitable. For me, although I get a good number of these of various sorts, it takes less than 5 minutes a day, and I take the viewpoint that it is a good professional-social gesture to make that quick response (perhaps more worthwhile than yelling over the phone at phone-solicitors on old no-caller-id phones).
At the same time, at the other end, I know many people who take the viewpoint that sending them email no more obligates them to a response than do credit-card offers and other advertisements. And, indeed, given the ease with which we can mass-email, even with customizations, this is a fair, not unethical, not harsh reaction. Perhaps if my in-mails of this sort reached 10+ per day, I'd give up "trying to be polite", but my own current scale of "spam on behalf of earnest beginner in the business" is pretty low, so I can easily afford to be (superficially) "gracious" enough to respond.
In case people don't reply, I'm afraid you can't hold it against them, even while we admit that it would be great if they did respond, ... because there just isn't a general social principle that demands a response to all possible inquiries one may receive. Yes, it'd be nice, but it is simply not required.

+1 for "It'd be nice, but it is simply not required"..

Maybe it should be required. Having grown up with email, it holds a similar weight as phone calls for me. Ignoring (polite and reasonable) emails is similar to picking up the phone, listening to the caller's introduction, and immediately hanging up. So yea, it's rude, not to mention unprofessional. Sending back a canned response does literally take only seconds, and at least gives the inquirer the feedback they need. If your time is so valuable and the number of wannabe-students so high that you can't manage, you are surely in a position where you can have your secretary handle things.

(My comment assumes that the original inquiry is not a canned message itself.)

@Raphael: No, it's closer to just not picking up the phone.

@JeffE That is true if it ends up in the spam filter or you delete it without even reading the subject fully. I strongly suspect, though, that the emails get opened and skimmed over (there might be something in there that warrants an answer, after all) -- that's listening to the introduction. It does not matter that the person intruducing themselves does not realise the mail is read. But then, maybe there is a generational difference in perception. (That said, not picking up your phone is certainly not a recommendable trait in a professional setting, wouldn't you say?)

That depends.  As a general rule, I only pick up the phone when my office door is open.  If I'm in a meeting, I don't pick up the phone.  If I'm in the middle of a task that requires uninterrupted attention (research, writing, preparing for class), I only pick up the phone for a few people (like my wife).  So basically, that means if you want to call me, we should arrange a time by email first.

@Raphael I guess that most people don't pick up the phone while at the office (at least it's my case). Concerning emails, I cannot answer within the day to those that require an answer, so I'm far from answering to unsolicited emails like that. And let me add that I spend more than 1 hour a day answering emails (it's closer to 2 hrs I guess).

@Raphael " If your time is so valuable and the number of wannabe-students so high that you can't manage, you are surely in a position where you can have your secretary handle things"  this is pretty naive.  It's certainly not true in academia or even in the corporate world.  Large organizations (universities and corporations both) often have convoluted bureaucracies to determine who gets an additional body for the express purpose of doing secretarial work.

@Chan-HoSuh Maybe I'm naive, maybe you lack cross-cultural awareness. At my university, ever professor has access to a secretary (depending on the department, each has their own). As far as I'm aware, that's representative of Germany overall. Note that I assumed that if you get too many of these mails, you are probably important enough to have access to a secretary/assistant. Of course my experience is limited; the situation may be worse than I imagine for professors at famous universities, even though they are not that famous/important (relatively speaking) themselves.

@Raphael I'm surprised you can accuse me of lacking cross-cultural awareness when I'm the one pointing out that making a universal claim like "important => has a secretary" is naive.  I'm certainly aware that is truer in some places than others.

I would say MOVE ON .. Some professors are full of students. They are not looking for new prospective students in the next year or so.
Therefore, the simple action to do is ignoring prospective students emails.
The best to do is to phone him/her if s/he didn't answer in 3 months after 2 or 3 emails. Try to meet him in conference and try to contact his/her current PhD students..

I am not sure how cold calls are taken. I don't want to seem desperate, but a one sentence email doesn't cost long.

Yes you are right.. but at the same time if the professor worth it, why not?.. Simply introduce yourself and the fact that you are interested in his research and has sent him several emails with no respond.. He might look again to his inbox.

I would consider a cold call very intrusive.  (See my reply to @Raphael's comment on a different answer.)

I definitely agree with you Jeff.. That's why I suggested the OP to move on and look for another supervisor.

Consider the possibitity of ending up in the spam filter. (I know a professor whos emails were regularly considered spam by his own university)
(As students of the supervisor are known: could any of those ask the prof whether any of the emails arrived?)
Students of the supervisor are known: this points to the group not being far away. Drop by in person?
One may use other communication channels  ("just wanted to make sure, my emails didn't get caught in the spam")

I don't think any of these are useful.  I think the most likely explanation is that the professor is busy, gets dozens of emails like this, and they are almost invariably a waste of his/her time.  See paul garrett's answer.  If that is the explanation, none of these is going to be helpful (they will just seem stalk-y).  The best angle is to figure out why you are trying to contact the faculty member, and then figure how to make it worth his/her time (if indeed it is; probably it isn't).

@D.W.: reading yours and other answers, I think this has a strong geographic/cultural component. And, I may have gotten it wrong, but I ended up with the impression that the student is closeby, i.e. either same university or a neighbour university (knowing people of the other group). Here (Germany) you often don't apply for a PhD program with a certain university, it's more like you apply for a topic with a professor.

Certainly possible, cbeleites!  I'm most familiar with US culture.  Do you want to elaborate in your answer on how the culture works in Germany or other areas you are familiar with?  That might helpful to many readers.


text:
Are there academic reasons to only use journal articles and books when writing?
Recently I was researching for a paper, but the results of my research got me reflecting on my habits:
Is is at all appropriate for me to use Google (partly also Google Scholar) for academic research, just because I have good experiences with it in my personal, non-professional environment? I noticed I feel slightly too comfortable in sourcing material via Google. As expected, the quality of the resulting materials is "bad", in the sense that the sources I happen to find are rarely journal articles and often chronically difficult to cite. Of course for many topics this is a non-issue, but for my current topic, a lot of government, international institution and NGO content was "on-topic" and needed, so that is how the situation came about in the first place.
While I definitely won't use Wikipedia or (online) newspapers, but I also came across e.g. OECD content: while the content itself is strong and academically valid, by now I sadly had to discard a significant part of it, also because I initially didn't (exclusively) use their "iLibrary". Specifically: The amount of time I had to spend trying to find e.g. the author of such non-journal content (and other source-data), trying to decide if I should invest my time into reading and citing the content vs. discarding it and that I have to enter bibliographic data by hand for such content make me tired.
Thus my thought is: Should I intentionally, sternly refrain/refuse to use (and of course cite) any materials that doesn't carry a DOI, ISBN or ISSN? There is still a lot of grey literature, manuscripts, working papers etc. and web content out there... My current frustration is so large that I seriously consider such a strict stance going forward, but I fear that I might miss out on crucial facts and that omitting such publication will affect the credibility and well-roundedness of my paper(s)?
In the age of Google I am very happy that academic standards are in place, compared to the lack of cite-ability etc. in documents published by NGO's, think tanks, policy institutes and some governments.

What a strange question.  There's a ton of utterly unreliable crap with a DOI/ISBN, and a ton of excellent material without.  An ArXiv preprint that's received (and been revised in response to) lots of community eyeballs is a far more reliable source than, say A New Kind of Science or a typical El Naschie journal article.

Dear JeffE, that is definitely true! Just going nuts regarding an ISBN provided by "The World Bank Group". What makes it worse that I can't find anything about their publication on the web, except, OK, the PDF itself (through one of their partner NPO's).

PS: Yep, strange question, I admit. While I agree about excellent material not sporting an ISBN/DOI, if I "just let it slide", I end up making myself extra work (such as when I didn't consult the OECD iLibrary first) and ending up with works that (like the WB example above) - currently - just exist at a single place (URL) on the web. Should I really cite such a publication? Additionally it might end up burdening the reader: "Citing publications used in research papers [...] are not exercises designed to strain the patience of writers." (http://www.libraries.iub.edu/index.php?pageId=2701)

If you use it, then you must cite it, and you must give the reader enough information to find it in principle.  So if you use a PDF that you downloaded from the World Bank's web site, then yes, cite the paper and include the URL.  Similarly, if you use a document in the rare documents archive of the Vatican library, then you must cite that document and point to the Vatican.

why not wikipedia? :) search for the "Mn3+ in Trigonal Bipyramidal Coordination: A New Blue Chromophore" (I don't have free access to it) and see that a very important discovery about blue pigments cites wikipedia...

Forgive me if I got this wrong, but it sounds like you are asking if you should limit your research to sources that are convenient to cite. I think you will find yourself missing out on significant sources and risk making anything you produce likewise irrelevant for not considering it.

Dear Mindor, no, you are correct, that is a big part of my question! As said, I also have those serious doubts that you mention. I know starting a "discussion" on SE is looked down upon, but there might be actually other reasons than "convenience" (e.g. for future readers to find my paper in a timely manner or at all) to only cite sources that are catalogued extensively.

Dear @JoshuaDrake, I changed the title to "Are there academic reasons to only use journal articles and books when writing?"

BTW: Once I cited wikipedia, see arXiv:1009.1031, as it is the most comprehensive source about Mafia (party game). However, it was only to provide general introduction, not to rely on it.

If you build your work upon other people's work, whether it be a blog post or postage stamp, then you should cite it, otherwise that's plagiarism. This is especially the case if the work is a primary source of the research (which can even be the case for blog posts).
That said, there are some guidelines you can follow to get the best version of the work to cite.

Find the most recent or most authoritative/official version of the work. If the paper is an unpublished workshop paper, is there a corresponding conference or journal paper that was later published? Or is the work perhaps written up in a masters or PhD thesis?
Find the primary source. Is the blog post (secondary source) a distillation of some other paper (primary source)? If so, go for that primary source. Is the Wikipedia article (tertiary source) based on some well-known book or article (primary source)? If the report from an NGO is original research (primary source) then you should cite it. If not, determine what it is based on an cite that.

Yes, give credit where credit is due, no matter the status/prestige of the source. In some cases I'd cite not only a primary source, but secondary or tertiary if they were (apparently!?!) essential to me in finding the primary source.

@JoshuaDrake: I just stated what the rules are, answering the question posed in bold -- at least, the cite version of it.

@DaveClarke Sorry for using the word "cite" and no offense, but I couldn't anticipate that everyone gets so hung up on it and assumes that I want to plagiarize (and ask permission for it on SE lol), how silly. (This is not my first post on academia.SE) If you want to answer a question on SE, you should, please, consider to read the whole text I wrote. I wrote it for good reason. The bold text was just my CONCLUSION from everything else I wrote. Aside from that, your tip "find the most recent or most official version of the work." is gold, I was never sure about this, I'll obey this now. :)

From my own personal experience, I have cited non-traditional sources that go far beyond the realm of books and articles, and even repositories like arXiv.org.
In some cases, these included "trade association" documents that cited chemical compositions for blends that we needed to have in order to set up a numerical model. In that case, the document was "official" enough that it could pass muster as a viable source of the data. Similarly, if one wants to cite a source like the NIST Webbook or an online database like the Merck Index, those are clearly curated well enough that one doesn't necessarily have to worry about judging its validity.
For sites that are not so well curated, then you do have to work as an arbiter of the quality of the website. You'll need to verify if there is sufficient data and evidence to back up the claims that you find in the documentation you want to cite, and if the document is suitable for citation, or if you need to dig further back to find better "original" sources. So long as you can "trace back" your work with suitable confidence, it's probably OK to cite a source from the Web. Once the provenance or accuracy becomes nebulous or tenuous, you should look for alternate (or more primary) sources.
To go the other way is, of course, also possible. The challenge will be that if there are very important sources of literature published outside the journal system—for example, government reports or other standard materials that "define" their field, then you will probably be called out if you omit them—and their findings—from your work. Now this may not be true in your field, in which case this won't be a concern. If you get a referee report with such a request and refuse to make the change on the ground that it doesn't have a digital identifier, you may find yourself with a rejection notice at the end of the day.

I frequently came across "trade associations" etc.  too. But my question was not "if it is appropriate to cite non-traditional sources" (I did that already), but if I could go the other way. (Still, I of course upvoted you.) My question is strange, I know.

I've added another paragraph to address your specific concern. For the most part, you're probably OK to ignore such literature. However, you are responsible for knowing the "critical" literature in your field, regardless of its source.

DOI, ISBN and ISSN are very useful tool for managing citations, but nothing more. You need to cite every material you rely on. Otherwise it is strongly against scientific ethics (i.e. plagiarism or intentional lack of acknowledgement).
Of course, when you use materials without DOI, ISBN or ISSN you need to put special effort to properly identify the cited material and to have any reasonable chance, that it won't disappear.
But for example arXiv ids, or even links to MathOverflow answers are good candidates.
If you point is "I refrain form citing anything without DOI, ISBN or ISSN just because" then, well, someone can pledge not to cite your journal, or just - any of your works, because why not (and it happens on the same moral ground)?

Even though this answer is a bit rhetorical-inflammatory, it does make an entirely legitimate point, namely, that ... "gosh", who decided what the "legitimate" sources were? :)  Once again, one might think about the non-identical-ness of "corporation-published with connivance of academics" and "significant scientific/scholarly progress". There is no longer any "academy" in which to have one's papers read out loud to the few dozen savants, as the only way to promulgate one's work, but/and there is an internet which creates difficulties in distinguishing glitter from gold.

Dear Piotr, thanks for the provocative ideas. You say "someone can pledge not to cite your journal, or just - any of your works, because why not (and it happens on the same moral ground)?", I say: Sure! BUT that is exactly why I ask here: I don't want to base my actions in this regard on "morals" or my own convenience, but I rather wondered if there are academic, scientific reasons to do so! Because as @paulgarrett said, someone "decided what the "legitimate" sources were". While I would say: No one decided that, at least not in my case, because: I said I cite anything with a DOI or ISBN. i.e.

(part 2), i.e. I didn't actually touch the "legitimacy" aspect at all! This is something I have to figure out myself, totally unrelated to the DOI etc. aspect - you bet I will. :) So ACTUALLY I would venture to say that today the "playground" is more level these days, as no one is forbidden to e.g. use an ISSN (free?), it is more that (which is also my criticism) most organizations don't even pay attention! If I have a paper of paid gov. officials in front of me, I expect them that THEY expect others to cite their work and thus make it easy and reliable for me to cite their work results.

@grunwald2.0 So there are two issues: is you want to trust/rely on a publication (which is up to your judgement; in particular you should not blindly believe just because of the stamp). BTW: books are typically not peer-reviewed; DOI does not guarantee it either. And looking only at identifiers in not a serious indicator or quality. The second is, if you rely on some result, you need to cite it. Period. (Actually, I meant "ethical grounds"). But still, I don't understand you particular problem. Could you clarify?

Interesting question. I think the answer lies in looking for what purpose you cite "anything but journal articles and books".
In this respect, it is important to distinguish between primary and secondary sources in research reports:

Primary sources are all items which were an object of your research, i.e., your research results directly stem from an analysis of these items. An example would be a text where you studied usage of a specific word. Or a telephone book, if you did a statistical analysis of telephone numbers. Primary references are rather rare in the natural sciences and engineering, but they would be more common in social sciences and humanities.
Secondary sources are items from which you cite research results in order to support your arguments. For example theories that you base your hypotheses on, reports on the validity of methods that you are using in your research, or other research results which you discuss in relation to yours.

Obviously, for primary sources, it doesn't matter whether they have been produced with academic standards or not. After all, they are the objects of research, and the validity of your research results does (in principle) not depend on the validity of the primary sources.
On the other hand, the validity of secondary sources is crucial for the validity of your research results, or at least your interpretation of the results. That's why you only want to use secondary sources which are up to academic standards, i.e. peer-reviewed scientific publications and books from established authors / publishers.
So the conclusion is that you should in fact try to refrain from using less credible references as secondary sources, while it will be perfectly fine to use anything as a primary source.

I said I want to cite ONLY journals and books (or any document type equaling those two formats) and nothing else. I basically want to NOT cite anything that lacks the credibility and "findability" of academic and scientific output that can afford to sport a DOI. ...I know the question is strange, but reading the question first before giving me a "noob-guide" about sources (assuming that I don't know that, sorry I do) would save you time. ;)

@JoshuaDrake I did so now. But I don't think " Should I intentionally, sternly refrain/refuse to use any materials that doesn't carry a DOI, ISBN or ISSN?" couldn't be any more direct! That people got hung up on the verb "cite" is not my fault. My question was never "am I allowed to NOT cite a source that I used for my paper?", a question that would as n00b and naive as it gets! Everyone knows they shouldn't do that. This is not my first question here on SE. But half of the answerers still made this assumption instead of reading my question properly! He assumed the OPPOSITE of what I asked.

@grunwald2.0 I guess my answer was not clear enough, and I tried to clarify. My previous last sentence didn't focus on the main point of the answer, and I hope this is improved now. I also apologize if the answer contains points which are very elementary to you, but I also try to write for less experienced readers.


text:
How to judge quality of manuscript to decide whether to submit to high-ranked journal?
I am not talking about whether I can submit a paper on subject A to a journal on subject B.
My question is:
How do I know how good my paper is? I could of course just send it to the best journal in the field, and see what they say, but I also don't want to embarrass myself and waste their time. If, however, it is very good and would be accepted by such a journal, it would be unwise to publish this in a lower ranked journal I would think.

Usually, you seek advice from someone who is familiar with your field and your specific area of work.  Most researchers start by asking their PhD advisors.

As a couple of others have noted, generally speaking you will get a feel for this as you read the literature in your field. However, your target journal may have published criteria for publication. For example, PLoS Pathogens states:

To be considered for publication in PLOS Pathogens, any given
manuscript must satisfy the following criteria:

Originality
High importance to researchers in the field
High importance and broad interest to the community of researchers    studying pathogens and pathogen-host interactions
Rigorous methodology
Substantial evidence for its conclusions

For most journals now, the reviewer is asked to score your paper against areas like this as well as provide general comments.
For comparison PLoS ONE states simply:

The study presents the results of primary scientific research.
Results reported have not been published elsewhere.
Experiments, statistics, and other analyses are performed to a high technical standard and are described in sufficient detail.
Conclusions are presented in an appropriate fashion and are supported by the data.
The article is presented in an intelligible fashion and is written in standard English.
The research meets all applicable standards for the ethics of experimentation and research integrity.
The article adheres to appropriate reporting guidelines and community standards for data availability.

Basically, as long as it isn't fundamentally flawed it stands a good chance with PLoS ONE.
The biggest differences between journals are typically how important your findings are, and to how many people. From personal experience the 'broad interest' criterion (where you are asked as a reviewer to comment on it) is the one I most often find myself scoring papers badly on; most people don't think about this enough.
Without wishing to sound negative: as the others have said, if you genuinely can't tell whether your own paper is 'good' then it probably isn't going to set the world on fire. Then again, nothing ventured, nothing gained; you won't generally get 'blacklisted' for submitting a low-quality manuscript to a journal, and it doesn't cost anything. So if you're being modest but are secretly quite proud of it, you might as well give it a chance with a high-impact journal first. You can always resubmit somewhere else if it gets rejected.
One final word of advice, since it sounds like you're fairly new to this: don't get upset, embarrassed or disheartened if your submission is rejected or torn to shreds by a reviewer. Rejection is common (especially if you're ambitious about the journals you submit to), harsh and apparently unfair reviewer comments even more so, and the editor will normally take the reviewers' side unless they're clearly in the wrong. (And if you stick with academia, you'll find this last bit this goes double for grant applications!)

Two things to know:

The top journals have very fast turn-around times. Instead of submitting your paper and waiting 6 months for a reply, you can submit it and find out in a few days that it has been rejected, and send it somewhere else.
Rejection rates are almost completely uncorrelated with journal impact factors: https://blog.frontiersin.org/2015/12/21/4782/

These two points combined suggest that the best strategy is always to go ahead and submit your papers to high-impact journals first.
This isn't advice that I have followed in my own career, but I saw it recently work for a young colleague who led a paper on which I am a co-author. He sent it to Nature, had it rejected in a few days, sent it to Science, had it rejected in a few days, sent it to Nature Geophysics, had it bounced back after a very quick review, and sent it to Nature Communications, where it was accaepted. All in all, it was published faster than any of my last few papers, all sent to mid-ranked journals. It was published in a journal that has (relative to the lead specialist journals in our field) a very high impact factor. It has had media releases put out about it as a result, and attracted some attention. And yet I would rate the quality of the content as no better or worse than any of my other last few papers.

There is no clear cut answer to this question; however, my suggestion would be that if you don't know how good your paper is then it is not good enough for the best journals in the field.
As an author I have always known what weaknesses my paper may have but it is not always possible to address such weaknesses in a timely manner. For the most selective journals in your field you should try to submit a bullet-proof paper. One that, at least in your own opinion, is not failing to address any possible issues.
Another point to consider is that top journals often expect more novelty than other journals and it is possible that they will not be interested in publishing work that is not significantly novel.