I'm in the middle of my exams at the moment and these are some ways I prepare. They might not work for you, but you can try.
When I am revising I make posters of the key points and stick them around the house in any place my parents don't object to. If I have a lot of names or terminology to remember I make revision cards, which i can easily carry around with me and look at when I am on the train or got 5 minutes to spare.
When I am revising I will take breaks regularly (maybe every hour). However, if I am practising an exam paper, I will set my self the time and do it straight through. Some peolple say you should take breaks every 20 minutes, but i find it pointless, as you can't get much work done in a session that short.
To decide what to revise if time is short I think of everything I can do well and ignore it. It can be temping to revise the stuff you know you can do, but is also is pointless. I think of my weaker areas and work on them. If I have a lot of past exam papers I will pick out the questions on that subject, try them, then check the mark scheme.
Generally, I find working through past exam papers can be good. You may know how to do the stuff, but if you have practised it one way and the question asks it differently it can be really confusing.
On the night before an exam I never stay up late working. I may read my notes, but normally I will watch a DVD or do something to get me relaxed. Like MathsIsFun, I try to get a good nights sleep.
On the morning of the exam I always have breakfast, even if I am feeling sick I will try and eat something, maybe just some fruit. I arrive early at the exam and sit/stand outside and go over my notes.
During the exam I work steadily and pace myself. If there is a question I am stuck on I skip it. If I feel a bit panicy I stop, take a few deep breaths and have a drink of water (I don't know if you are allowed to take a bottle of water into your exams).
Also don't do too much revision as all you will do is tire yourself out and forget things. I've been through that, didn't realise I was doing too much at the time, but was really exhausted afterwards. For me it was trial and error finding out how much i can do.
I hope some of this helps, and good luck with your exams.