Collaborative tools for dummies/professors Suppose that coauthors from two or more different institutions are writing a paper in latex, and would like to do better than repeatedly emailing drafts back and forth.

They realize they can open for free a dropbox account, share the password, and synch the version of the paper on their computer with the one on dropbox. If two people are simultaneously editing the same section, however, they'll overwrite each other changes.

They have also heard that version-control systems like SVN and Git have tools to merge concurrent changes, which work reasonably well. The documentation of these products, however, is rather hard to read, and it is more focused on how to undo changes and how to manage different "branches" rather than on the basic needs of coauthors writing a paper.

Is there a simple step-by-step exposition on how to use a version-control system in this setup:


 central repository
 local copies
 "smart" merge
 no branches


?

Of the standard version-control systems, which one is the easiest to use? (We are talking theoretical computer science professors here.) 

Are there even simpler tools that  only do synch with smart merge, without version control?

Conversely, do people who use version-control systems to even write a single-authored paper really feel that the unlimited-undo capability is worth the extra complexity?
First off: If your are interested in real-time collaborative editing, try something like gobby. It lets you literally edit a document at the same time.

As for revision systems, I am only familiar with SVN. This is what you do, after installing subversion, of course:


Get someone to set you up a repository and give you URL, username and password
Go to where you want to have your lokal copy
In a shell (command line?), type: svn co url://to.your/repository (check-out). Now a new folder with the repository's contents appears.


That's all. Now the most basic commands:


Whenever you add a new file foo, enter: svn add foo
Whenever you want to remove a file, enter: svn rm foo
Whenever you have made changes, enter: svn ci (check-in)
Whenever you want to get the newest stuff, enter: svn up (update)


There are also commands for moving, copying, branching, resolving conflicts,  ... but as long as you do not try funny stuff, you are fine with the above. If anything breaks or seems to, backup your edits, delete the whole folder and checkout the whole thing anew. That's for svn like rebooting for Windows.

Addendum: I see you seem to be concerned about "smart merges". I assume that you refer to have to different versions of a file merged, with the assumption that two people added things in disjoint parts of the paper. As far as I know, svn would treat that as a conflict, and probably rightly so. I don't think that there is a general procedure that ensures you get what you want after two people manipulated the same source. There are graphical svn clients that visualise such conflicts and help you resolving them; they are pretty much diff-viewers were you can choose which version to keep for every conflicting line). It will require work, though.