While reading for GMAT, I came across a book called Thinking, Fast and Slow. It discusses an effect called priming. If you keep your lips straight or curved up as if you are smiling, you will do positive things (such as, rate a movie higher). Our brains can be primed to turn to one direction.
For this reason, try to keep a positive and happy attitude through out the test. Keep a little bit of time in the morning to do a few questions (priming). i.e. Don't schedule the test too early in the morning, thus not allowing yourself to have a relaxed start.
Slightly off topic, but relevant nonetheless.
Kudos is the best way to say Thank you.