1.) First off, relax. Be confident in yourself, but not arrogant. Make yourself believe and think that you will do an amazing job. While taking your exam, imagine you are at home alone, with you goldfish and your dog.
2.) You are probably feeling the urge to practice all the time, since you feel insecure about your playing. But, believe it or not, don't over practice. Over practicing will lead to your memory and skills receding, because when we learn, our brain 'memorizes' all of the movements, the notes, and the dynamics unknowingly. Over practicing will diminish this amazing ability that our brains have.
3.) Concentrate on the things that you have trouble on. Drill them into your mind, like it's become a part of you. Don't let yourself get distracted. For the scales, here is a great way to memorize and get the hang of them (daily exercise):
1. Two octaves, HS, quarter, beat= 84, 100
2. Two octaves, HT, quarter, beat= 84, 100
3. Two octaves, HS, eighth, beat= 84, 100
4. Two octaves, HT, eighth, beat= 84, 100
5. Two octaves, HS, sixteenth, beat= 66, 69
6. Two octaves, HT, sixteenth, beat= 66, 69
7. Two octaves, eighth (RH) against quarter (LH), beat= 76, 84
8. Two octaves, eighth (LH) against quarter (RH), beat= 76, 84
9. Two octaves, triplet (RH) against quarter (LH), beat= 76, 84
10. Two octaves,triplet (LH) against quarter (RH),beat= 76, 84
CHALLENGE: Two octaves, triplet (RH) against eighth (LH), beat= 76, 84
Two octaves, triplet (LH) against eighth (RH), beat= 76, 84
4.) Get a good night's rest every day before the exam. Starting now, go to bed earlier than you usually would. Study has shown that after practice, sleeping will help your brain process all of the information that is has taken in. You will see a significant difference in your playing, and you would be surprisingly better at the thing you had trouble on the day before.
5.) Don't worry about it too much. Worrying will just make your stress peak grow even higher, and you will tense up too much while your playing. Relax, and practice like you would any other day. Just focus on what needs to be fixed, not how well or how bad you will do on the exam. Zone out into your little world when practicing, and you will fine.