Make sure you get plenty of sleep. When I'm tired I tend to drive erratically and on my test day I woke up early due to noises from outside (only got 5 hours of sleep). In the last 2 or 3 minutes of the test I pulled out of a junction when there was a car but the examiner braked. I failed as it was a serious fault. If I waited I would've passed with 5 minors (2 were for speed). Get plenty of sleep, drink a red bull (or an energy drink of your choice), use the toilet before your test, get practise just before your test, don't panic, pay attention to everything and check your mirrors. Also react to what you see in your mirrors, e.g. don't turn left if you see a cyclist coming up the inside. Remember you can go off route if it's done safely.
Wish you luck!