I probably cannot offer anything that has not been mentioned above except a few things I've learned.
1. Nothing, absolutely nothing replaces either training in a martial arts or self defense class.
2. Training builds confidence in your abilities. I don't mean a snotty attitude either. Trained fighters don't need to prove anything. As a matter of fact, they seem calm to an outward observer and they are calm. You WILL learn your strengths and weaknesses and everyone has them. You WILL get an inner confidence. Calm confidence is a powerful deterrent, not a beligerant attitude.
3. Keep relaxed, a stiff body is wasting energy. Again this comes with confidence in your ability. It also slows you down.
4. Do NOT worry about the outcome or getting hit.
5. If punches fly, let them hit your arms. They are wasting energy.
6. If or WHEN you strike, the nose, the throat, the solar plexus(wind) are your targets.
7. Now this is the hard part to understand. If you strike for the nose, your focus is not the nose, it the back of your opponents head. You are punching through the nose to the back of the head. It is the same with the throat or wind. Your focus will be the spine. even though your target was the Adam's apple or ribs.
You do NOT need to draw your fist back to do this. Your fist strikes from wherever it is as fast as you can make it go, but your focus is behind the target. Your strikes will be devastating. Do not stop until your opponent has stopped.
8. If you use your legs or knees, aim through the knee caps or drive the groin area up into the chest. What I'm saying here is DON'T stop on contact, follow through.
What I have just described here is very violent and maybe nauseating, but this is what fighters do. Personally, I do NOT want to fight anyone. I DO NOT want to hurt anyone. Do I know how to hurt someone? YES. I hope I never have to with all my heart.
9. Repeating #1. Nothing replaces training in either a martial arts or self defense class.
I wish you well.