When it comes to actually learning about subjects, such as math, science, literature, etc, there are a variety of efficient methods to go at it. Most notably, of course, is smart note-taking. Taking notes normally can be a pain to reread and understand, but smart note-taking takes care of that.
The first step is to add more blank space. Adding more blank space between separate sections of notes allows a much easier time when reading back through. The second step is to clearly label different sections, as well as putting the date next to when the notes were taken. Clearly labeling different sections does not mean, however, simply adding an extra line or two. Add in a solid inch (two and a half centimeters for those of you who use metric) of blank space between the title and possibly add some different colors or some other dazzling effects. You'll increase your note legibility infinitely more than before with these two things.
All credit for note-taking tips to my Algebra-based Physics teacher.
Extra link for even more tips for notetaking