Just do it man! Tell her how you feel what you like about her then ask her on a date. Or being mister cool/romantic guy and sing or rap her a song with good emotion and maybe get her some flowers. Also be very confident don't loose your voice
Just wait for the right moment to tell her But what ever you do DON'T do it over Facebook, text etc. from a girls point of view it just shows that he's not brave enough to tell her. and DON'T get your friends to do it for you just ask her to the movies or bowling and just be yourself.