Okay, it requires some confidence, it's like Russian roulette but a friend of mine opened quite a few sets with this:

He was with at least one friend/wing. When he spotted a girl, he - with a big smile on his face - raised up straight his arm pointing at her with his index finger and kept this position until the girl realized him. Of course he did it when he was in front of but a couple of meters from her so it was easier to spot him. When the girl saw him, he started to count down with his fingers 3-2-1 then waved his hand to "come here" (like Neo in Matrix). 90% of the the time the girls shook their head indicating no but then my friend just turned away to his friend/wing. Surprisingly high number of girls approached him within a minute despite shaking their head a minute before.

It's crazy, you cannot do it too many times at one place but it's fun and works.