Who decides if a verse is literal and what parts of the Bible metaphorical? Just to be clear, I'm not asking what parts of the Bible are literal and what parts aren't. I just want to know who decides which view verses are supposed to be followed and which ones are like obsolete.

For example, verses like these are not followed anymore. 

Leviticus 19:27:


  You shall not round off the side-growth of your heads nor harm the edges of your beard.


Leviticus 11:8, which is discussing pigs:


  You shall not eat of their flesh nor touch their carcasses; they are unclean to you.


Genesis 38:9-10:


  Onan knew that the offspring would not be his; so when he went in to his brother's wife, he wasted his seed on the ground in order not to give offspring to his brother. But what he did was displeasing in the sight of the Lord; so He took his life also.


Leviticus 19:28: 


  You shall not make any cuts in your body for the dead nor make any tattoo marks on yourselves: I am the Lord.


Leviticus 19:19:


  You are to keep My statutes. You shall not breed together two kinds of your cattle; you shall not sow your field with two kinds of seed, nor wear a garment upon you of two kinds of material mixed together.
  Likewise, I want women to adorn themselves with proper clothing, modestly and discreetly, not with braided hair and gold or pearls or costly garments.


So I'm wondering how can people choose to disregard these verses anymore and still be a Christian... if so, then why is it still in the Bible? Who decides if something from the Bible is obsolete? Because as what I have observed, people tend to disregard parts of the Bible if it doesn't fit the current trend anymore like the haircut thing and the fabric matching... So is it people who decides that these verses are "OK" not to follow?
I'm going to answer your stated question: &quot;Who decides wat is literal and what is metaphorical?&quot;  That's a legitimate question.  The old &quot;what laws are still in effect&quot; has been answered many times.  Hence my VTC.  What is metaphor and what is literal, however, is a good question.

Ultimately, who &quot;decides&quot; is a verse is literal or metaphorical is the person reading for himself.  Any given text can be interpreted figuratively or literally - indeed Gregory of Nyssa (Life of Moses) could pull allegorical meaning out of the feathers on the quail that piled up in front of the children of Israel, and John Dominic Crossan can dismiss the Resurrection itself as mere metaphor.  Indeed, even the existence of David, the King of Israel, was long considered only myth, until archeological evidence proved otherwise.
This is true in any reading endeavour - when reading a news story, for example, most people assuming that news stories represent a literal meaning, except when you are a {liberal | conservative} talking about {Fox News | MSNBC}.  And then, of course, there is The Onion :)
John Searle's work on &quot;speech-act theory&quot; is often considered in the midst of apprehending meaning from a text, and is one of many starting places in hermeneutics. In basically suggests that every apprehension of meaning is ultimately an act of the mind to ascertain the genre.
Denominationally, two primary approaches to reading Scripture prevail:

Dogmatic Interpretation
The Catholic Church in particular stresses the dogmatic concept of Scripture. As the institution charged with guarding Scripture, they have developed traditions about what is literal and what is metaphorical. As the repository of the keys of heaven, the church is particularly suited to settling matters of interpretation, ensuring a regula fide that does not change over time. It understands that there is a multitude of meaning in Scripture (see the Catchechism ), and stresses the importance of reading Scripture in the traditional context to avoid &quot;novelty&quot;. It does not necessarily see this as an either/or question.

Priesthood of All Believers
Protestants tend to favor provate interpretation (&quot;What does this mean to you?&quot;), although especially amongst the earliest reformers, the tendency was to require that &quot;private interpertation&quot; be run through your fellow believers so as to avoid twisting Scripture into meaning things it didn't. To avoid mis-reading, one should submit one's own interpretation to the whole body of believers, so as not to distort the meaning of the text.


Those are the primary approaches - but ultimately, even the camp you decide to fall into, is a matter of personal choice.
Beyond that, however, &quot;editing&quot; the Bible just isn't a possibility.  While there are differing positions on the &quot;inerrancy&quot; of Scripture, preservation of Scripture (the idea that God has given us the Scripture we need) is not nearly as controversial.  What has been handed down is that the 'canon' of Scripture is merely a list of those books which Christians over the centuries have found most profitable.  It is nothing more than the NY Times Best-Seller List. (See this for more). There is no process for changing that list, because it is simply so set in stone.  Over time, certain emphases are more important to different generations, but as a matter of doctrine, the idea of preservation says that we have all of what we need - even if some of it is more fashionable than others.