Determine the theme, or focus, of your essay. Write the theme in one sentence. If you cannot state your theme in one sentence, you probably are not clear about what you want to write. Determine the purpose and readers for your essay. Maybe you intend to inform car enthusiasts about the history of a particular automobile model, persuade them that Car A is better than Car B or relate funny incidents involving the Batmobile used in movies. This is the material for your introduction. If you correctly analyze your readers and have a topic of interest to them, you should have little trouble gaining their attention.
Organize the body of your essay into units or major ideas. Develop a set of organizing ideas to guide your thinking. An organizing idea may be as simple as past, present and future. Explaining what features cars have now that they didn't have 50 years ago and then predicting what features they will have in 50 years that we don't have now will make a well-organized essay. Other simple organizing idea are best and worst, right and wrong or doctors, nurses and patients. For a persuasive essay consider a problem-and-solution organizing idea. Make a list of the reasons many people in the United States don't have adequate health care and propose changes which address that problem. Explain why enforcing a particular law is unfair to some people and how the law should be changed to benefit everyone. For each part of an organizing idea, state evidence that supports it or examples that illustrate it.
Conclude your essay by restating the theme you want to leave with the readers. For a well-organized essay, this last step should flow smoothly. Note that this article's organizing idea -- introduction, body and conclusion -- is stated in the last sentence of the introductory paragraph.