What should i do, there is this girl i like?

Basically there is this girl at college that i really like, i might even be Mosby-ing her (HIMYM reference). but a friend thought it would be a good idea to ask her if she would consider going out with me if i were to ask her, he didn't ask her out for me i hasten to add, and she said no. But i really like her what should i do and how should i go about it as i have never had a gf before.