I would never throw the first punch.
Now, I personally see that as stupid. If someone does decide that they want to start a fight, 90% of the time they "talk themselves into it." By that, I mean they start talking a whole lot of BS. Once they announce their intentions and get close, I have no compunctions against hitting first. I also know when that isnt an option (inside the house at a party, when the adversary is 12 and I'm 19, etc). What I am saying that I dont throw away that option just because.