Revising the night before an exam won't get you a great mark, it will just stress you out. Revision is meant to be done gradually throughout the semester, so you retain what you just learnt in class.
Revision starts at school
The more attentive you are in class, the less work you have to do at home. If you ask questions, clarify things you don't understand and take notes in class, you're halfway to passing your exams.
Use your notes
One of the simplest revision methods is reading over your notes and textbooks. However, you need to process the information in a way that helps you remember it.
Summarising is a good way to do this. Write down key points in your own words, and note any ideas you don't understand, so you can clarify them with your teacher.
Looking at old exams helps you predict the kinds of questions you might get in different subjects, so you can plan your revision accordingly. If you write sample answers from these exams, you're going one step further. Ask your teacher if they have time to critique your answers so you can improve before your real exam.
Study groups and tutors
Set up a study group with friends so you can critique each other's work. Try to pick people who will help you focus, not distract you. If you need extra support and can afford it, personal tutors can also be a big help.