So, i've tried this is the field and its worked everytime.
Disclaimer: I've only tried it out at house parties.

Anyway, its really simple.
the target should preferably be isolated.

You just go up naturally and say "You look bored!"

You raise your relative value by asserting that she is bored. If you successfully pull it off, you communicate that you are having fun and can show her a good time. Also, it gives you an opportunity to do something fun with her- which can lead to a crazy night (maybe a truth and dare?)

Another good point about this opener is that you will notice that she will try harder to make your night fun. She will feel like she needs to legitimize the fun youre having and try to trump the experience you were having before you opened her.

Try it out, it works like magic.

It obviously works better if you're ACTUALLY having fun. So please boys, be yourselves, be natural and spread the love.