I have not as of yet, nor is it likely i will ever, gathered the balls to perform this one, but urban legend among my friends has it that one of my boys did it, with predictable results.

Look around a bar until you make eye contact with a girl...that shouldn't be too hard. Once you have established eye contact, crook your pointer finger and wiggle it in that standard way that indicates you want someone to come over. While this sounds like the hard part, it's actually easy, as curiosity, if nothing else, will often get them over. At that point, as (i believe it was Tolinka) someone mentioned, it's all in the delivery: as she comes over, likely across a semi-crowded area if it's a good place, curiosity should really be eating at her and she'll come up to you and say "yeah?", or "what did you want?" something to that effect. As soon as she says that, and without hesitation or looking at your "boys", reply, "I just wanted to see if I could make you come with one finger...imagine what i can do with the other nine and a whole bed to work with!" At this point brace yourself for any number of things, ranging from a nice little slap to a genuine laugh and some interest.