I think it depends on what subject it is.
For me personally, I have a very visual memory. I draw pictures of ROOMS, like a house room and then draw posters/pictures on the walls/ceilings with lines between them, I then memorise this room and when I'm in an exam I can literally 'look' around the room and read what I need off the walls.
Other than that it's literally just do a past paper, find what you suck at, read up on it, do some notes, do the notes again then answer some more questions on it until you improve.
HTH.

.