My advise it to chill for a bit and break up the revision into small parts, if you're the unorganised sort then drawing up a revision timetable might help you.
What you do is first write down the days you want to allocate for revision (this may be all week or you may want a day off) then decide how much time on each of those days you have for revision including time for breaks, split it up and fill in the subjects that need revising A few tips:
[*]Don't try to do too much at a time, your concentration is high at the start, dips in the middle, and picks up again towards the end, so the longer you do at once the more your concentration dips in the middle. I'd suggest 40 mins revision with 10 min breaks inbetween but you'll have to find one that works for you.
[*]Leave some free spaces in your timetable, either in case you have to miss some of you revision time for some reason, or if you you find that a subject needs more revision than you allocated it time for.
[*]Be careful how you arrange the subjects, if you know you don't like writing then don't schedule two writing subjects right after each other. All that will happen is you'll lose interest and your concentration will drop. If you're doing more than one foreign language, it may be an idea to have a gap between them so that you don't get muddled up. What I tried to do was mix up the subjects I enjoyed with the ones I didn't (although you may find it's the ones you don't enjoy you need to do most revision for.)
[*]Try to complete your revision a week before the exam, after then you can do short reminders (10 minutes or so) but nothing large. Otherwise it's less likely to go in, and more importantly you'll end up getting stressed that the exam is in a few days and you still don't know everything.
[*]If you are getting stressed, stop immediately and find a way to calm down, I can't help you here, you'll have to find something that works for you. However I will say that if you try and do revision while stressed, you'll learn virtually nothing.
Finally, it's very important that you know how you learn best, if you're a visual learner then writing out a load of text isn't going to help you learn very effectively, you be better with diagrams and mind maps. Likewise if you're more auditory than speaking things, and recording them using a dictaphone or similar might work better. Your teacher or someone else at school should be able to help you with this.
My last tip, is to try and learn everything as you go along. It may mean more homework and a bit less free time, but you'll be thankful for it at the end if you find you don't need to do a ton of revision. I learnt that the hard way, trust me on that one.
Here is an example revision timetable and more tips:http://wordpress.mrreid.org/2009/12/18/how-to-make-a-revision-timetable/
(ignore his point about colour coding if you like, in my opinion it only takes a few extra minutes and makes it easier to see when you're revising what)
Lastly, feel free to PM me if you have any specific questions.