I've been in my fair share of altercations but there is a few unwritten rules that I go by..
Never kick someone when they are down, never go for the eyes/throat/jewels with intent to injure (I'm not talking about punching someone in the face, I'm referring to eye gouging, and other gutless moves). If the guy has stopped fighting back, that's it... it's over.. I'm not going to beat the living crap out of someone to prove a point. I have rarely ever been the instigator, but because I grew up a bit faster then most of my friends I was the 'enforcer' in our group... You know the guy who sticks up for his drunken, idiot buddies? lol