Here are a few tips:
1sr rule. Be a good man/woman. Don't ever steal and don't fight innocent people no matter what. Look people in the eyes when you talk to them. If you end up stealing from that person, you will no longer be able to look at the person in the eyes with confidence unless you are skilled at lying and stealing. But even so thieves have to live their life in fear of getting caught. Try very hard not lie too, when you are not honest then you have to make up more lies to cover the previous lies. Everyone tells white lies sometimes especially to wife and girlfriend , but it best to be completely honest and tell people the hard truth upfront, and not live in a lie. If you are good person then no unnecessary trouble will come for you. But if are a bad person karma will bring twice the trouble for you.
2nd rule. Learn martial arts from Bruce Lee. His fighting style is name "jeet kune do". And is probably the most effective way to fight. Remember to "move like water" and use your momentum and legs to add extra power to punches and kicks. Buy a boxing bag and practice. Try to learn the best from other martial arts styles and techniques and practice with you best buddy when drinking :)/
Hitting the gym sometimes helps, but having big muscles can slow you down in punching, while it is a big aid wen combat becomes very close and opponents are grabbing each other and wrestling.
3rd Rule. That is the all you need to focus on and practice and as well as eating good food. When you are not working out try to remain calm and not angry, don't let stress get to you. Stress will make you triad and more week. If you feel there is a fight coming up for you try to remain calm at all times, only a few seconds of anger when you see your opponent should do it then. Action speaks louder than words. If you are angry enough at someone that you want to rage and shout at them, don't waist your breath shouting, either beat bad people up straight away or walk away from a fight which is not necessary. Shout at people only when you are giving then another chance to understand you before you beat them up. Otherwise don't shout angrily at people.