Fights at school sometimes happen. But how can you keep away from a fight? Here's something you can do.
Be calm (冷静). Sometimes, you feel so angry that you really want to teach somebody a lesson. But being angry can't solve problems. Neither can a fight. Instead, it may bring you more problems. In the school, everyone involved (卷入) in a fight will be punished, no matter who started it. There are no winners in a fight.
Shout loudly. If you know someone is coming up behind you to attack, turn toward the person with your hands up in front of your body and loudly say "stop" before walking away. Loud voice can usually make the attacker calm down. If the person doesn't stop, cry for help by calling out the name of a teacher whose office is nearby.
Your friend may ask you to join in a fight. Learn to say no. Helping him fight is not really helpful to him. If you really want to give him a hand, try to ask him to give it up. Also, you can tell him if he gets involved in a fight, he may get hurt and be punished. Then, try to learn why he wants a fight and help him find a right way to deal with the problem.