I like wildonsquats reply, usually there is less fighting involved than peope think, also I agree with louden in general, wrestling techniques can come in handy. Most of the toughest SOB's I know have good wrestling background, you can pound on their face and they will never let you go....eventually you get tired and they beat on your face....
My best advices from experience- be fast enough to get out of the way of the drunk a$$ haymaker 99% of them always decide to throw... then throw them in a full nelson and smash their face into every door and brick wall you can find on the way out....
In case you do need to duke it out, strong lifts in the squat, clean push press, and a 400-450lb bench couldn't hurt in your pursuit to turn someones face to hamburger (if they stay on their feet that long)