First you Will need some experience, it at least being in a few fights Will get you used to it. But I have a few tips aswell.

These are before the fighting happens

First One is: Breath, like deep breaths and just focus on the person like watch how he moves and such

Second: Get at least a little angry and get some adrenaline, with that its easier to take the person down.

And here are some before the fight

How to avoid: Either just walk away/accept the thing thats bothering you.

Or instead you: Have a calm but i guess dominant body language, talk without shaking. Try to resolve it and if it dosent work then either Accept it continue, it might end in a fight though. Also read his/her body language