Do the hit and run technique... Go up to them and say, "listen, I have to go now, but if i didnt say this, i would regret it all week." then say they they are really good looking, seem like they are a really nice, warm hearted person, and someone who you could picture having a good time hanging out with. be honest (IN A NON THREATENING,NON STALKER-LIKE MANNER, if you look shady, this wont work) and then say that you just had to get that off your chest and begin to leave. This puts the girl in a position where she must make a quick decision, basically a use it or lose it. if she had no interest, you can exit and just be glad you did it. the positives are that she gives you a number and that could lead to more. the worse that could happen is that she makes fun of you (then you say, i guess i was wrong), and its ok, since you are leaving anyway.
Start off asking if she likes to suck dick. Most girls love this approach. Then say that she would look really good barefoot and pregnant. Throwing in a few lines about her making you dinner and bringing you fresh beers when you are sitting on the couch in your underwear also give an air of confidence.
I forgot right now. We had a liquid lunch at the only mexican restaurant in downtown Indy (which still sucks). We ordered the 48oz margarita and they brought us the 64oz'er. I am quite forked up right now. I will be lucky if I finish my work at this rate.
Just mention the Rockets or Lord of the Rings. That always projects a positive image, leaves em panting.
Go up to her and wisper the dirtiest thing you can think of in her ear. If she doesn't slap you then you know she's interested. This seems to work for Bill McNeal.