I have a fifth comment which will probably be irrelevant by the time Vahn sees it, but this goes to all you other silly peoples should you be giving an oral presentation or some-such! :O
Get a good night's rest BEFORE the big presentation/exam/whatever.
Prepare all you want, but generally* you work better if you've slept well and had some R&R for your brain to reboot and internalize everything you've so diligently tried to prepare for. If nothing else, you'll walk in without feeling miserable, which is a plus if you at least start off the presentation feeling good about yourself.
*
If someone brings up a story about pulling an all nighter, and getting an A+ on something, this does not apply to you. You are obviously a superfreak. Sing the song and do a dance.