I agree with several posts on getting the info on the early side of things. Most men hang on too long and wear out their welcome, completely ruining the challenge/mystery thing by 'showing all their cards' the first night and seeming too eager, interested, or desperate. If she really likes you tonight, she'll really like you tomorrow. If she doesn't, it's a waste of time, anyway.
Respect her time and the fact that she is out with her friends. If SHE does the inviting and seems genuinely interested in having you hang, then by all means, hang with them. But in general, less is more.