Outlines tend to proceed down a page, using headings and bullets to structure information. A common system consists of headings that use Roman numerals, letters of the alphabet, and Arabic numerals at different levels. A typical structure would be:
I. First main topicA. Subtopic
1. Detail
2. Detail
B. Subtopic
II. Second main topic
A. Subtopic
However, this sort of structure has limitations in written form since it is difficult to go back and insert more information. Adaptive systems are used for paper-and-pen insertions, such as using the reverse side of the preceding page in a spiral notebook to make insertions. Or one can simply leave large spaces in between items, to enable more material to be inserted. The above method is effective for most people, but you can be creative in making your own method. (See Category:Outliners for more about application software that supports outlining.)
However, computerized note-taking, whether with a word processor, an outliner like Workflowy, or a digital notebook program such as OneNote, EverNote or TiddlyWiki, provides the opportunity to revise easily and add more entries or rows to the outline.