Remember that writing course you once took, the one where you learned about pre-writing activities, the importance of drafting, and the need for revision?  That course was designed to help you with all your writing, yet a surprising number of student writers fail to apply its wisdom in their other courses--they invest little time in pre-writing, and they tend not to revise in any meaningful way, which means they are essentially turning in rough drafts.

Many papers never really get off the ground because too little time is spent in pre-writing.  Pre-writing involves such techniques as brainstorming, free-writing, clustering, nutshelling, outlining, mapping, etc.  It's the time before any formal writing begins, when you're thinking and jotting down ideas and (especially) re-reading and re-re-reading the work you're going to write about.  This is the period when you're selecting a topic and narrowing it down and formulating a preliminary thesis.  It doesn't matter what technique you use, but it does matter that you determine which ones work best for you, and that you use them.  The one thing you must do, though, is re-read.  It's only when a work of literature becomes familiar to us that we can really begin to notice the details of it, to pay attention to the way the author has constructed it.

Drafting

Some people start their writing with what is called a "discovery" draft--a very, very rough and rambling draft in which they have little idea of what they want to say and so write to discover their topic and preliminary thesis.  If you write a discovery draft, you should probably then write a second draft, a true rough draft, that you can use as a basis for revision.

The rough draft is a full draft of the paper.  The bulk of the writer's attention is on the ideas, the argument, the evidence, and to a lesser extent the structure--but not the prose style, the grammar and mechanics.  Student writers tend to invest too little time on the former--mistakenly believing that they can just "fill in" the details of the argument and the evidence supporting it later--and too much on the latter.  Don't expend energy polishing what's going to be changed later anyway.  Work instead on exploring ideas.  The draft is the place where you can digress, pursue a point in detail to see what it will yield, examine a variety of different passages--in short, to over-write.  Students rarely believe me, but it's much easier to revise an eight-page draft into a five-page paper than it is to revise a three-page draft into a five-page paper.  Once you've got your ideas down, you can then step back and look at the paper objectively, determining what, exactly, you want to argue, what the most effective structure for the paper is, what the best evidence is, etc.  If you only sketch an argument or leave out sections of it or put off including evidence, all you're doing is converting your "revision" into a rough draft.