Ask her on a date or to prom? Please Help

There's this girl I've had my eye on for a while and I was just wondering if I should ask her to a movie as a first date, or just ask her to the prom instead. The prom is 2 months away, but everyone seems to be looking for a date now. And I don't want some other guy to ask her out to the prom because I really want to be with her. Or I could go out with her a few times, starting with a movie, and ask her to the prom later. What should I do? I really fear someone else will get to her first because she is so beautiful. So if I'm going to make my move, I'd best do it now before it's too late. What would you do? Thanks in advance.

Stop posting, ask now worry later. You people waste so much time wondering if they'll say yes, by the time you get to them they'll already have a date and you'll REALLY be stuck cause you'll then have to look for somebody else. It's not a lifetime comittment damn it.

EDIT: There I polled.

I plan to ask her out to SOMETHING by the end of this week.
I just need to know what you think is the better idea to do first.
But I do plan to ask to her out very soon. Just tell me what you think by answering the poll. Thanks.

I say since your pressed for time 2 mo is really short just got to ask. If not I say go with date first to get to know her a bit then slip it in during the date not the next day. I found that to many times I wait a little while long could lose the mood ha ha.