Identify at least two main points you plan to include in your essay to support your thesis. The longer your essay, the more main points you will probably need. Assign each of your main points a Roman numeral. If your essay includes five main points, list the Roman numerals in order: I, II, III, IV and V. You may include your introduction and conclusion as main points in your outline or simply state your thesis at the beginning of your outline. Either method is acceptable unless your instructor has told you to write your outline a specific way.
Choose the sub points, major details and minor details you want to use to develop each of your main points. Each main point should have at least one sub point to support it. Assign an upper-case letter to these sub points. Within each sub point, list at least one major detail or example you want to include to illustrate that sub point. Assign an Arabic numeral to these major details. To flesh out your outline even more, think of at least one minor detail you would like to mention to develop your major details. Assign a lower-case letter to each of these minor details.
Format your outline correctly. Include periods after all Roman and Arabic numerals and upper- and lower-case letters. Since Roman numerals include different numbers of characters, make sure the periods following the numerals line up. This will keep the spacing in your outline consistent. Indent your sub points one tab, your major details two tabs, and your minor details three tabs. If this spacing doesn't appeal to you, replace one tab with three to five spaces. The Purdue Online Writing Lab provides a sample of what a correctly formatted Roman numeral outline should look like.