Whatever subject you are studying, a good approach is to come home at the end of the day and review your notes. Anything you don't understand, formulate into a written question so you can check on it yourself or ask your teacher or tutor for help understanding.
Waiting till the night before an exam will likely make you nervous. It will be hard to have enough time to prepare. Study a little each day, then, cramming can be helpful. Be sure, however, that you eat and rest well. Especially the night before a test, go to bed early. Eat a good breakfast before an exam, too.
Review a bit every day, then, the night before, quickly review what you've worked on, then, get a good rest. Maybe, you will have a miracle because you have prepared yourself a little bit every day.
(c) 2012 Dr JSS