To write an outline in APA style, use Roman numerals for main headings and capital letters for sub-headings. To break an outline down further, use Arabic numerals, lower case letters and Arabic numerals. Outlines can be written in fragmented or full sentences. Often, a decimal outline format is required. To achieve this, use full numbers as main headings, decimals for subheadings and double decimals for further subheadings. For example, use 1.0, 1.1 and 1.1.1.
When writing a full sentence APA outline, an appropriately cited APA reference list must be included. If any quotations are used in the outline, they must contain in-text citations.
Well-written outlines contain parallelism, or a consistent structure within headings and subheadings. If initial headings are started with verbs, all following subheadings should follow suit. All headings should also be coordinated and should have similar significance. While subheadings should also be coordinated, they naturally contain information that is less significant than that in the heading.
Headers are general statements, while subheadings contain specific responses to the headers. Every heading should have at least two subheadings. Subsequent information can be added to the subheadings. Avoid dragging the information into too many subheadings, as new headings or subheadings outside the normal APA style may have to be used.