Begin at the end. Write the body of your essay first, omitting the introduction until you have completed your argument. This allows you to review your essay and prepare an introduction that accurately reflects the arguments you present.
Outline your main points. Your essay should include a series of main points and supporting materials to back up those points. Make note of these points in the order in which they appear in your essay for use in your introduction.
State your thesis. A thesis statement is a one-sentence summary of the overall argument of your thematic essay. If your essay argues that America's entry into World War II ended its policy of isolationism in foreign policy, your thesis statement should make that claim clearly and concisely.
Explain the main arguments of your essay. Following the thesis statement, you should list the main points in the order they appear. Following the example made for your thesis statement, you might write: This essay compares pre-World War II U.S. foreign policy to post-World War II foreign policy by exploring these three points (briefly outline your points).
Preview your conclusion. Many thematic essays respond to a question. Make sure that your introduction gives the answer to the question. For example, if you attempt to answer a question about whether World War II ended U.S. isolationism, you must establish the basis for your answer in the introduction.