Look at the examples in the media section here (or others, if you have them). Particularly the winning essays!
You can search the papers for the essays. As a start (and not to say ours was any better than the others) here is the link to MOE's:
http://www.chiefdelphi.com/media/papers/1983
If I am remembering it correctly, we used the sections outlined in the Executive Summary to organize and write the essay, then wrote the Executive Summary based on the essay. Other teams might do it the other way around.