How should I go about asking a girl to prom?

I guess you could say she's sort of a valley girl but she's als got the brans. Anyway, I'm afraid of other guys getting dibs on her before me so I plan on asking her about a month before the actually day..you know, something she'll always remember. I realize it sounds pretty cliche but she means a lot. Also, I'm a senior and I've seen it all from a giant banner, to a giant cookie, a locker full of plastic play pen balls with a note underneath saying 'Sorry I didnt have the balls to ask you out in person', to a locker full of peanuts with a note underneath saying 'Sorry I didnt have the nuts to ask you out in person.' so please provide originality, thank you in advance:)