Keep all your notes for each class together and organized.
If you know where to look for something, you can make better use of your notes for the current class and in later classes.
Review your notes for a class within 24 hours of taking them. Use this review to expand any abbreviations you used while taking notes and to rewrite any thing that is illegible. Studies show that you will forget as much as 2/3 of what you learned within one day.
Review all your notes for a class on a regular basis. Do not wait until just before a test.