girls!!!!! what's the "best" way of getting the girls number?!?

I've only known this girl for maybe about 3 days but I've thought she's the prettiest girl in school since last September. I added her on fb yesterday so things are moving but slowly. I'm lookin to taking another step and getting her number. Since its the long weekend I won't be seeing her till Tuesday, I was thinking I could maybe get my "texting game" going. My only line of communication with her ATM is Facebook so I was thinking about asking her for her number over that. I feel like that may seem cowardly as opposed to asking for it in person. What would be the best way to get the girls number. I mostly want to know the girls pov