Sleep Well the night before a test (minimum of 8 hours)
Eat a well-balanced breakfast the day of a test
Bring multiple pencils in case one breaks
Use the bathroom before testing begins
Avoid distractions
Answer the easiest questions first
Read all directions
Don't be afraid to ask questions if your are unclear of the directions
Never leave blanks (if you can help it)
Avoid Second-Guessing yourself.  Your first thought is usually your best one.