If you have taken your notes in shorthand then write them out properly. Many notes, especially when out and about, are scribbled down in haste so you need to make sure you will understand them at a later date. Once you have done this and have the content clear in your mind, cut them down so you are not reading through stacks of irrelevant information. The more concise they are the quicker you can read them and grasp their content.
Read through your notes and underline key words or phrases. Highlight the different themes so that by looking at them later you instantly know what they are relevant to and the most important bits. Your notes should be an aid not a full blown account of every fact and argument. Less is definitely more when it comes to note-taking.
Organizing your notes is key to them helping you when you need them. If you have saved them online make sure you have a backup copy. If they are in paper form put them in a clearly marked file. You should organize your notes from when they were written and what they were about. This will make it way easier to locate the notes you need come revision time. If you are keeping paper copies a color-coding system will be a big help. This may seem very 7th grade, but it really is the easiest way of helping you to memorize and compartmentalize your notes in your mind.