Ahh, I know this one. :)
Short awnser: I make a thesis first, than an outline and try to keep a solid argument throughout the entire essay.
Here is the long awnser, my method I use in school currently:
First step, develop your thesis. A thesis is a provocative statement that requires proof. i.e. Yedda is a useful website that enables internet users an opportunity to share virtually limitless information.
Second step, decide on three points that prove your thesis. Put these in an outline.
Third step, write your introduction, ending with your thesis. Start each new paragraph (or section) with a new point from step two. Put your most powerful argument last.
Fourth step, write a conclusion that sums up your three points and restates your thesis, but in different words.
Also, take a look at the following link. There may be more information here than you're looking for, but it is worth a brief look anywho.
http://www.aucegypt.edu/academic/writers/
And if your still looking for more, check this site out. It has everything.
http://owl.english.purdue.edu/owl/resource/557/01/