It helps draw (and keep) your attention when you review your notes.
A few guidelines:
This is what some of my notes look like:
(I’m not sure this will help anyone, but it’s my main method to get myself to do something for school, so I thought I’d post it anyway. Aside from the fact that you’re more likely to study off of material that looks nice, I really like making things look pretty, so the whole formatting and structuring thing lets me get familiar with the study material while I do something that I enjoy.)