If your opponent uses dirty tricks, there's no reason why you should hold back. When in a planned fight, you and your opponent should come to a mutual agreement of what is and isn't allowed in the fight. You can also get an impartial third party to help lay down the rules and act as a kind of referee for the fight. correctly. Before you even think about throwing your first punch, you need to have a perfect fist. Curl your fingers inward onto your palm and make sure your thumb is on the outside, folded across the bottom knuckles of your first few fingers. If your thumb is on the inside of your fist, you are likely to break it. Unlike a street fight, letting your foe make the first move is a reasonable strategy. Make sure to avoid every strike you can and spring back with a counterattack. It's important that you keep your body in motion, making punches difficult to land. A proper fighting stance will also make you harder to hit by creating a smaller target. Instead of facing your opponent head-on with your shoulders in parallel, stand to the side with your dominant half forward. You won't be able to dodge every punch. For the hits you have to take, absorb the shock as best as you can to make them less effective.  When taking a body blow, brace for impact by tightening your abdominal muscles. Shift your torso so that your opponent's fist lands at your abdominal muscles to the side rather than at the center near internal organs. For blows to the head, flex your neck and jaw muscles and lean into the punch. Make sure the hit lands on your forehead, which is incredibly tough. Above all, never let a strike land at your temple, jaw, or nose. Although it's not generally acknowledged, there is an unspoken rule between men that strikes to the groin aren't acceptable in fair fights. It's considered to be a dirty trick along with other actions like eye gouging and hair pulling. If you come out on top with these methods, your friends are unlikely to consider it a legitimate win.  Weapons should also be off-limits unless...

TL;DR in Chinese:
开始之前定一套清晰易懂的规则。 正确地握拳。 防止对方击中自己。 如果实在躲不开，尽量减轻打击造成的伤害。 不要使用卑鄙的伎俩和可能致命的动作。