sleep

whatever you do, make sure you're getting enough sleep.  i just finished four years of sleep-deprived high school and it sucked.  i'd suggest looking into the research that dr. james maas, a professor at cornell who has done extensive research on the effects of sleep on the body, both mentally and physically.  from personal experience, i can say definitively that the more sleep i get, the better i play.  it's easier for me to concentrate and i notice a difference in my play.  the amount of sleep needed varies slightly from person to person, but research suggests that EVERYBODY needs a minimum of 7 hours per night for optimum performance.  in teenagers, this goes up to 9 1/4 hours of sleep per night.