Paragraph 1: First sentence: Your thesis statement. Follow it with several sentences that back up different aspects of your thesis. Write a paragraph for each of those supporting sentences. The first and last sentence of each of those paragraphs should be the original sentence stated a bit differently. Last paragraph is a restatement of your first paragraph.
It sounds like a lot of repetition, but once I started following his advice, my writing quality improved vastly. It tends to impart a razor-like focus to the writing. Not to mention that the systematic quality of it almost makes it feel like the paper is writing itself.