Everyone has their own ways of remembering things, but there are some good general points that might help you out.
If you just read over things, you might find that you can’t remember much at the end of a session. It’s helpful if you make notes for yourself, writing down key points in your own words makes it easier to remind yourself of later.
Drawing diagrams and sketching things out can help fix things in your memory, especially if you’re trying to revise something complicated.
If you make sure you can explain each concept you go over out loud, or on a piece of paper, you’re more likely to be able to remember it later, and you can make sure you’ve understood things properly.
I find that I remember things a lot better if I write notes by hand instead of on a computer.
Remember to take plenty of breaks; it’s hard to stay focussed for long periods of time and you’ll end up working more efficiently. It helps if you move about, and do something different away from your books or screen for a few minutes.
Revision can be really stressful. It helps if you make a timetable beforehand, and give yourself plenty of time to cover everything.