Knowing the bouncers is probably the best thing posted in here, as not only will they help you out if the guy came with 10 friends (likely the reason his insecure ass can't pick up any women!), in addition to the fact you might get to stay in the club while the other guy is tossed, to finish your drinks and enjoy your night.
I remember one time in Montreal when a guy jumped me on the dance floor with sucker punches cuz I stole the girl he had been working on all night, one bouncer I knew just grabbed him and asked 'you want me to take him out the backdoor to the alley so you can handle it there?'
Not getting into fights is smart advice in this day and age though. Too many wannabe gangsters can easily get themselves a glock and wait for you outside the club.
Despite it often being fun to get into an old fashioned bar brawl, rare are those who fight that way anymore or rarer bars that let it go on (I mean one on one, with whatever is around you, drunken type fight). It's something I had to learn here, to walk away since chances are high I'd just get shot or stabbed quickly by some Colombian coke head out here.
Luckily, being a big guy and with tatoos and piercings, not many people even try to start anything with me. They'd rather pick on a pretty boy or quiet guy or small guys (even though I as well have seen many small guys kick a bigger guys ass)