"Nobody wins a fight" - Dalton, Roadhouse
If there's one thing that I've learned in the few years that I trained in Kung Fu, (many, many years ago) it's that you can prepare yourself for a fight if one is coming, but looking for one is never a smart option.
(I'll take from your name that you might actually be 13 years old, and I'll address your question thus because of it.)
As you are 'preparing' for a fight, first think about these things:
Why are you fighting? Is it to prove yourself? To prove a point? Is this the school bully, who's going to whup your ass every time if you don't stand up to him?
What brought on the fight? Were you acting all tough and saying, "Hey, this guy ain't so tough - I can take him." Were you 'called out' to fight him?
Why can't you walk away? Can you talk it out? Is there some reason you have to fight?
My most important thought is this. What constitutes the end of the fight? (For him, and for you!) And, before you quote 'gypsy rules', are you sure he's going to be a 'gentleman' about it? When you're fighting, there are no real rules, so who's to say he's not going to get pissed and try to humiliate you?
Think of this - you take his hits, land your own, and are the 'winner' (see my quote above). The crowd you draw is all over your win, cheering and the like, and you feel like 'Big Man'. He's on the ground, bleeding, and gets up while you're recieving all your glory.
He pulls a knife out, sticks it in your back, punctures your kidney and kills you. ...it happens more frequently than you would think.
Have you ever noticed that Boxers, Ultimate Fighters, Kickboxers, etc. always have a Referee to make sure that the fighters fight fairly, and that they're never injured beyond repair?
Food for thought.