Proper striking method

Punching someone in self defense seems to come as a normal response. Something you see every day on TV. I do not recommend doing so. Even for the trained individual, punches can go bad. You can hurt your wrist, break a finger, your hand. Subtle movement can make you miss your target and let you connect with something much harder and too much for your little hand to handle.
For those who are not trained, an incorrect punch can definitely put you in a bad position and create a serious injury.
There are other options that much safer, better and deliver as much or more power into your attacker:elbows, palm strike, knee strike….
Learn how to use those correctly and deliver enough force to be effective.