I love it when people try to pick fights with me. Here's what I do:
When the guy comes up all loud style trying to fight, I stand up, throw up my hands, and virtually yell in a big broadcasting voice:
"HEY, HEY! I DON'T WANT ANY FIGHTS BUDDY! HOW ABOUT WE GO UP TO THE BAR SO I CAN BUY YOU A DRINK INSTEAD."
Then gesture towards the bar. If he accepts, follow at a distance and shoot a bouncer the "WTF are you waiting for" look.
This does four things:
1. Alerts everyone in the bar to the fighter - including bouncers. The bouncers know that you don't want any trouble, so you're in the clear.
2. Makes an a55 out of the guy for trying to pick a fight.
3. Potentially diffuses the situation by confusing the fighter. "... uh... what?.... more booze? Free?... duh... OK." Sometimes the fighter cools out and actually buddies up to you. Mad social proof.
4. Since you made a big scene, everyone turns around to watch - including all the ladies. Since you had a smooth resolution, all sorts of openers just fall in your lap. After the drink with the fighter (if he isn't thrown out before you get to the bar), be sure to capitalize with the ladies.