Make mind-maps on posters and stick them around your room and read them occasionally, so you absorb the information over time but it stays in your head longer. Doing them in colour also helps.
Write out exemplar answers to questions and learn as much of the mark scheme as you can.
It sounds a bit silly, but teach the topic your learning to somebody else (or to a stuffed animal). It begins to make more sense to yourself when your the one explaining it out loud.
A ton of past papers.
Watch some videos on youtube and listen to podcasts. I'd go crazy if all I did was just read endless notes.
Good luck!