There are four very easy things you can do to improve your ability to punch effectively. That is, with more risk to your opponent, and less risk of injury to yourself. If you've studied fighting at all you probably already know these basics, but they bear repeating.

  1. Learn how to make a proper fist.
    First, do NOT put your thumb inside of your fist. This does not help, and makes it likely you'll hurt yourself, so don't do it. Open your hands wide, and curl the fingers into a tight ball. "Tie the ball down" with your thumb. Curl your thumb into itself. You want to strike with your knuckles, not with your fingers. You also want to strike directly, not with the side.

  2. Learn how to lock your wrist, so that your hand and forearm become one.
    When you strike something, the weakest point of the arm doing the battering is the wrist. It is also easy to injure. By locking your wrist, your make your fist and your arm into one. A battering ram. If your wrist gives, your power goes into it, instead of your target.

    I find that doing push-ups with your hands in fists instead of spread out is a good way to learn how to lock your wrists, as well as building wrist strength. You get a real sense of the fusion of fist and arm that is necessary.

  3. Punch through your target.
    This ensures that you follow through with your full power. If you stop short, you're depriving your punch of power for no real benefit. Aim at imaginary point behind your opponent and try to hit it as hard as you can.

  4. Punch in straight lines.
    Swinging around may look neat, but it's not nearly as effective as punching in straight lines. Also, swinging around leaves you more open. You can throw a punch more frequently and more directly if you keep it tight.

    Throwing darts is a good way to practice this. Accelerating the dart on straight line before you release it increases your accuracy and is the same basic motion as punching in a straigh line.

Now combine these steps. First make your first. Curl tight. Picture a straight line starting at the knuckle of your index finger and extending through your elbow. Lock your wrist to make the line. You are driving this straight line through your opponent.

Practice, practice, practice.

This w/u is in the public domain.