Last minute revision is often very counter productive, especially if you've revised in advance; I prefer to relax with a book or a game of cards before an exam
Preparation as mentioned above already. Positive thinking, if you've prepared well then you know you can do well so believe in yourself, don't allow any negative thoughts to creep in. Keep the day stress free, get up early and be at your exam hall well before you need to be. Nothing makes you more stressed than if you've had to rush because you're late. Eat well before the exam, but nothing new as you don't want digestive issues, and take a bottle of water with you even if you don't think you'll need it.
Also experiment with different types of revision such as flashcards, mind maps, lists etc. This way, you may find a revision method that fits you best.
Also, do not spend every second of the day. This will stress you out more so make sure you leave some time to relax and have fun with friends, as well as revising
Hope that helped in some way!