How should I increase my mental acuity for a standardized test?

This wednesday is the only day that i can take the PSAT in order to qualify for the national merit scholarship. I don't want test help, or practice, I'm fairly confidant i can achieve the scholarship as long as some mental fluke does not occur. I'm asking for advice on how to make my mind work at its peak for that day. Obviously more sleep is good, and I'm a runner, so I bet running that morning will help me that day, but after this I'm stumped. What should I eat for breakfast? Any vitamins recommended? Is Caffeine good or bad for the day? How much sleep should I get (I have 5 nights) Any other suggestions on what i should do to achieve peak performance mentally?