FTR, b/f approaching a chick, look at her body language? What is it saying? If she's all back turned, and in some kind of girl huddle, leave them alone.
However, if they are in an more "open" and relaxed position--GAME TIME!
Granted, experience has taught me that 1 out of 20 chicks have egos as big as sky scrapers, and think that EVERY guy is hitting on them.
When this occurs, I have three routes of action:
1. Start laughing hysterically, and say, "you think I'm hitting on, I am so sorry, I truly didn't mean to lead you on like that...." and start walking away.
2. If she's a complete bitch (after a while, you can just "tell"), run the bitch shield buster, "I'm sorry, I thought you looked like a friendly person, my bad"
2b. If that still doesn't get an apology or satisfactory response, go w/, "I'm sorry, is your personality your form of birth control?" Then walk away. Childish? Yes, satisfying, absolutely.
....and if you really want to rub it in, add a shooing motion w/ your hand. I once had a HB9 absolutely go BALISTIC ON ME, and I starting crying I was laughing so hard.

Then had some other chicks who hated that girl, start hitting on me as a result
