Think of a topic and decide on how you want to develop this topic.
Decide the main topic and subtopic. The main topic and subtopic must be related, meaning, they have the same idea. The subtopic is an expanded idea of the main topic. You can expand the subtopic by adding supporting details.
Remember the symbols. a. Romal Numeral is for main topic (I., II., III.….). b. Capital letters is for subtopic (A., B., C., ….). c. Arabic numbers is for supporting details (1., 2., 3., …). d. small letters are for more supporting details for supporting details (a., b., c.…) – if you will want to further expand your outline.
First letter of main topic and subtopic and even the supporting details must be written in capital letters.
Don't forget the period after the Roman numerals, letters, and Arabic numerals. You might be asking if you could add another level or more level to your outline. Definitely, you could.
Remember the alignments and indentions. (Look at the two-level outline.)