Disclaimer: if you attempt this you responsibility i hold no legal responsibility to the info posted herein)
Be aware of your environment. Aside from various objects that can be used as weapons and traps, knowing where to run is very important--especially when you're outnumbered. Use all of your senses fully. Don't just look around directly--use shadows and reflections to your advantage.
Err on the side of caution by assuming the following: Your opponent is a better fighter, and has backup; They have a blunt or edged weapon, such as brass knuckles or a knife; and you will be hit. Be ready to take a punch.
Walk away from the fight. Although perhaps obvious, the most sure-fire way to "win" in a street fight is to not fight one altogether. In the vast majority of cases, there will be some sort of warning before actual physical aggression occurs. If you can resolve a dispute without having to fight, do so. Don't let your ego get in the way of your safety. In a verbal dispute that has the potential to become violent, stay calm and take a firm but apologetic approach. Be neutral and non-confrontational. For instance, if a guy accuses you of looking at his girlfriend, you can just apologize and say that she looked like someone you used to know. He now has only two options:
Accept your apology, and maybe even apologize back. If this happens, all is well. Is it that hard to apologize to some jerk (even if you don't mean it) to avoid a fight? If the situation seems to be resolved, remember never to turn your back on the aggressor. It is wise to take 2-3 steps backward and then turn. Always be ready for a sucker punch.
Continue the threatening behavior. If he continues to threaten, repeat the apology. Look sincere, but not weak! If he continues to threaten and close the distance on you, say that you do not want any trouble. Be firm verbally. Use terms like "back off" or "keep away". Get louder as he gets closer.
Stay at a distance from your opponent, allowing the distance to shorten only to strike. The attacker needs to close distance to strike you. Staying just out of their reach means they cannot hit you. Try to stay on an opponent's 'outside' (i.e. towards the side, rather than directly in front). Remember that they can be an obstacle to themselves. Keep your guard up. Even if it's only by extending your hands in a 'stay-back' type of pose, it places something between you and your opponent.
Know when and how to run:
If you are outmatched or outnumbered, or just not willing to fight, then run at the first opportunity towards public, well-lit areas where there will be others. When escaping in the middle of a confrontation, try to impede your opponents as much as possible:
Block them with obstacles. If you can put a trashcan, car, bus, or policeman between you and the attacker, all the better.
Run between narrow paths, such as between cars on a parking lot, run up a narrow stairwell and fight downward (make sure you have an exit), or run (and fight) through a narrow hallway. This will prevent the opponents from ganging up on you.
If you know you won't outrun them, don't try. If you are caught (especially with multiple attackers), you will lose the fight due to a simple lack of energy. The one or two opponents that sprint with you may be just as tired, but those jogging behind will be fresh for the fight.
Establish your balance so that you can stay on your feet. Spread your lengths to shoulder width and bend your knees. Going to the ground is very dangerous to the untrained fighter, especially if the opponent has weapons, back-up, or ground-fighting experience. If you find yourself tangled up with them, break away any way you can.
Defend yourself. Respond to attacks by aiming for any open, vulnerable spot without exposing too much of yourself. Use "reasonable force" (see Warnings below).
Damage to "soft spots" (face, temples, throat, kidneys, solar plexus, etc.) may eventually incapacitate your opponent. Scratching, biting, clawing, spitting, pulling hair and attacking eyes can also be used. You are defending yourself from a violent aggressor, not fighting in a ring with rules. Use anything you can to ensure your safety. Poke the eyes, and if there are others ganging up on you, hit with outstretched fingers into the front of the throat.