To do well in exams you must first learn the material, and then review it before the exam.
These are techniques to help you better understand your material:
Learning
It is important that you take good notes whilst in your classroom as you will use your textbooks for most of your revision.
Review your notes soon after your lesson.
Review notes briefly before the next lesson.
If possible spend some time at the end of the week reading through your notes.
Reviewing
Take good notes
Organize your notes, texts, and assignments according to what will be on the test (if your teacher can tell you)
Estimate the hours you'll need to review your course materials.
Draw up a list that blocks units of time and your course material.
Test yourself on the course material.
Finish your studying the day before the exam. You won't learn anything by revising the night before - its probably too late by then - so sit back and have a well earned rest!