Just approach and tell him, "You're such an eye candy, wanna be my boyfriend?"
Seriously, here are some suggestions:
Get to know and befriend him by talking to him in class or joining a club he's in. Send him a friend request on facebook. It's normal to be nervous around someone you like, but don't pretend to be someone else just to get the boy. Be friendly to him whenever you see him.
Don't look easy or slutty.
Once he starts showing an interest in you, play hard to get. Guys find such girls more attractive. Pretend as if you're not really interested in him or you're too busy to pay attention to him.
Happy boy hunting. 