i would have to say protien. however, being 18 myself, i kinda disagree and would have to say.... sex, yeah, sex and porn. Cause after you get laid your head tends to swell slightly and you get a nice ego boost that just makes you feel good about yourself.
So, increase your protein intake, eat lots of food, and have lots of sex. Just make sure you dont have sex with the daughetrs of guys who juice, otherwise you might find a hyperdermic needle in your ass, or throat. just a word of caution. and remember this "If your not gonna wrap it, go home and wack it."
Ross