I second the above post and say fighting is a last resort. The only exception is law enforcement and security types. However, then, the purpose is not to fight, but control your suspect,patron,oppenent.
My philosophy has always been in a streetfight is unavoidable, as in the defense of yourself or loved ones, all rules are off. Your goal now is to disable your oppenent as quickly as possible with minimal amounts of harm to yourself.
Others may talk about technique, fancy styles, years training, standing or grappling. I like to simplify it.
KNEES, GROIN, THROAT, EYES. Those are the only targets you need, and attack them by any means neccassary. You can't walk, breath or see and you can't fight. If somebody has a hold on you, grab thier groin or eyes, they'll let go.
With any use of force, you risk injuring, maiming or killing another. Be sure you need to use it if you do use it.