Use a consistent structure in your main headings and your subheading, constructing subheadings in the same way you construct your headings. For example, if you start one heading with a verb, start every successive heading with a verb.
Coordinate information in headings and subheadings, making sure the information contained in each main heading has equal significance.
Use subordination in your headings and subheadings. The main headings should present general information and the subheadings should present more specific information related to the main headings.
Use Roman numerals to identify main headings and capital letters for subheadings; this is called an alphanumeric outline. You also can use Arabic numerals and lowercase letters or a full-sentence outline, which is set up like an alphanumeric outline but features full sentences for each outline level.