Hi there,
As with most learning, we all have our own ways of working and techniques that work best for us. It is also dependent on the subject you are revising. With subjects where you need to remember factual information (like biology and chemistry) revision cards, mind maps, quizzes etc can work very well.
With essay based exams, past exam questions are useful and again, mind maps.
Ask you teachers for any past exam papers they might have!