Stilts

That's the problem, most guys want to just say a little something and have women fall all over them. "Hi" is a great way to start, then build it up from there. If she says hi back without even looking at you, like trying to ignore you, then you can usually move on to someone more interested (or try to batter down the walls, which can be fun too ). If she says hi and pays attention to you, then you follow up with a question about the music, or the bar, or just about anything.

After a couple of minutes of small talk then look around a bit and tell her you really need another drink because you're empty. Tell her that your friend said he'd be back in a bit, and you don't want to miss him. "I'll make you a deal, if you do me a favor and keep an eye out for him for me, I'll bring you and your friends back a few drinks with mine" That puts her in a position where she's helping you out and she'll feel better about letting you buy her a drink even if she's not terribly interested in you, more of a trade. When you get back, she'll usually talk to you while she's drinking just to be polite if for no other reason, but it gives you more time to convince her that she really should be interested in you.

I'm not suggesting that you use that situation as some kind of line either. What I'm saying is that you need to arrange for her to spend enough time with her so that you can convince her that she really wants to get to know you better aka another date, or a phone number, sex in a car in the parking lot etc. You can use a pool game, asking her for help picking songs on a juke box, helping her get away from a guy that she's obviously not interested in, anything really where you get more time, and she doesn't feel that you're all over her being creepy.