Guys relate to people by doing things with them. When you see him and his friends doing something, ask if you can join in. Sports work best.
Also, try talking with the guy. Find something you want to talk to him about and see if you can start up a conversation. Or ask him for help on something. Few guys will pass up a chance to help a girl. Again, while he's helping you, start a conversation, find some common interests.
Don't try dressing in skimpier clothes. You'll get his attention, but he won't be able to think of you as a friend.
Let him come to you. Wear long hair, short skirt, some cleavage and he will find an excuse to come to YOU.
Ask a mutual friend to introduce you guys. Then start talking to him more often and calling him your buddy and stuff. And after you have been friends for awhile, call him your best friend (as if you are joking around). After awhile, you will start to act like best friends.