I hate the way school bangs on about revision instead of just trying to teach you the damn stuff in the first place. In my experience in maths and science, 9/10 times if you have gone over something in class and understood it then, you will remember it. In essay subjects, practice questions help but if you're not up on the basics like structure, grammar, actually understanding the question you might want to go over that first. You can't revise for drama, history urrghhh, bad times for me but I still got a B by cramming as many relevant names and dates as I could think of in there and by already doing a practice question almost identical to the exam one. In French I tripped up on the little connecting words like to, of, on etc. I did maybe 10 hours of staring at revision guides, did all my coursework on time and got A*A*AAAAAABB.