Some examples of a standard outline format are the alphanumeric format, the full sentence format and the decimal format. The Purdue Online Writing Lab has descriptions of each type and a link to samples, as of 2015.
The alphanumeric outline format is a common standard that uses Roman numerals followed by capital letters, followed by Arabic numerals, followed by lowercase letters, to show the hierarchy of organization. A Roman numeral is followed by a word or phrase denoting a theme of a paragraph. Under this theme is a list of ideas lettered A., B., C., etc. Lower ideas under these follow the same pattern using the alphanumeric standard. Each lower stage on the hierarchy is indented further from the margin than the higher stage.
The full sentence format uses the same system but implements full sentences as thesis and idea statements. The decimal format has the same organization as the alphanumeric format but uses Arabic numerals exclusively. Decimal notation separates each sub-theme at every level of the outline.