How long have you known him for? Maybe you should give yourself some time to just be friends, especially since you don't even know his sexuality.
I have to agree with the above statements that it almost never works out if you try to push yourself on him and he doesn't recipricate your feelings. I've lost friends in the past because I read the messages wrong and pursued something that wasn't really there.
If you still want to find out, you can always going drinking with him and get a little buzzed, try to make a move, and then blame it on the booze if it doesn't work out in your favor. Just say, hey man, it was the beer talking, not me!
Note: I just saw that you're not the legal age to drink, so I am not condoning underage drinking. Booze and drugs are bad. M'kay!