Smile. Compliment him. If you know anything about him, start a conversation on a topic he likes, such as music or cars or sports. Most of all, be yourself; don't ever turn yourself into what you think someone else might like; that's not the real you they like, in that case.
Not that I was ever any good at this, but if you have any mutual friends, couldn't you ask them to hook you guys up?
Just be yourself. If he notices you great, if not, then there are way more fish in the sea that you will like even more. If you attempt to be something your not to get him to notice you, it will never work as a relationship, just a one night stand.
if you look like your avatar(pict) he noticed you, he is poss feeling the same, go up and talk to him, what do you got to loose, if he doesn't like you i'm sure there is a truck load of guys that would, don't be stuck on one guys acknowledgement of you, plenty of fish in the sea.
well if you miss out on him then i'm sure in time you will get to know someone better, i know that doesn't help right now, but your hottie, don't forget that, you may get someone better, hell your young don't get tied down anyways, you will have plenty of time for that, have fun, when your young beat the hell out a life cuz when your older it wants to beat the hell out of you, have a great time....
Say hello to him. OR ask him out.