One thing I forgot to mention in my earlier post about exam techniques:
If you have to do an oral exam (and almost everyone has to do some kind of speaking task), whatever you do....DON'T BE QUIET. It's fundamentally important to try to do the task as best you can, even if you think you're going to sound like a fool.
Why? Examiners cannot tell the difference between someone who's too scared to talk and someone who doesn't understand the task. In the end, a silent candidate is someone who is not doing what he or she was asked to do, and that means guaranteed failure.
So...take a deep breath. Smile. Talk, talk and talk some more, and if you're doing the exam with a partner, be sure to talk to your partner, too. After all, your failure is NOT guaranteed (unless you stay quiet, of course...)