We've looked briefly at four different formats for taking notes:
Formal outlines
Headings Followed by Lists (Informal Outlines)
Basic Notes
Graphic Organizers
You decide which format to use based on several factors:
Whether or not you have a starting point to determine the hierarchy of information (e.g., a teacher's outline, headings in a book chapter, a meeting agenda, etc.)
Whether or not you are already somewhat familiar with the subject matter
In the case of taking notes at a lecture, whether or not the speaker is well-organized and presents information in an orderly manner versus skipping around
Whichever format you use, always apply Principle #1: "Don't make everything look equally important.