just...incase you wanted nemore advise,
dont run through it fully in the hour before you do it, it lets you calm down a little. and remember, the teacher marking you is there to support you, not tying to mark you don as much as possible!
find people that you know to look at from time to time to see how well your doing, and be prepared to do something you would never dream of doing in an essay, digress. thats if your doing your chosen topic or work experiance etcetc. if the class/teacher havnt experianced your topic in the same way as you, then you can digress all you want, and theyll neva know, as long as you do it with confidence!
if your doing a character one, then dont worry too much, im sure you would have read the book they are in dozens of times, dont just concentrate on who they are and what they would say, ut how they would say it, im not saying put on an accent, but just where to stress words.
trust yourself, and use that adrenaline rush that you'll get to your advantage, it'll make it more intresting if you do!
hope some of that was helpful, and good luck!