Rules to Survival
1) Stay balanced - when power punching stay balanced. Always maintain proper striking form and do not overextend your body when deliver punches and strikes.
Remember that losing your balance in a self defense situation can cost you your life! 2) Be mobile - avoid the tendency to remain stationary.
This doesn't mean that you have to dance around like Muhammad Ali, just move around strategically and vary the speed and direction of your footwork. 
3) Stay relaxed - avoid tensing your muscles when punching.
Tensing your muscles will slow you down significantly and also lead to a possible injury. 4) Throw different combinations - avoid delivering one strike at a time.
Learn to harmoniously integrate your kicks, punches and strikes into devastating compound attacks that you would apply in a street fighting situation.
Keys to Success!Punching Power Rule #1: DON'T LOCK YOUR ELBOWS. When throwing linear punches, be certain not to lock your elbows.
Elbow locking is a common problem among martial art novices. When delivering a linear blow, your arm should be extended toward its target until the elbow is not more than three inches short of full extension.
After contact is made with the target, the fist is returned back to the hand guard position. Remember, if your elbow locks upon impact, it will have a pushing effect and rob you of critical punching power.
Punching Power Rule #2: USE YOUR THREE POWER GENERATORS.
When executing hand techniques from a stationary position, there are three anatomical power generators that will allow you to torque your body maximally. They include the following: (1) shoulders, (2) hips, and (3) feet. Maximally torquing your body into the blow will increase both the force and penetration of the blow.
However, there is a very fine line between power and speed in relation to the three anatomical power generators.
Punching Power Rule #3: YOUR LINE OF INITIATION IS YOUR LINE OF RETRACTION. When executing linear blows (lead straights, rear crosses, finger jabs, palm heels), remember that your line of initiation should always be your line of retraction. Avoid arcing or dropping your blow.
Such sloppy body mechanics will throw you off balance, minimize your impact power, and open you up for a possible counterattack. Failing to maintain a straight-line trajectory is usually caused from the following: (1) your elbow does not travel behind your punch, (2) premature wrist torque.
Punching Power Rule #4: DON'T TELEGRAPH YOUR PUNCH. Telegraphing means inadvertently making your intentions known to your assailant.
There are many subtle forms of telegraphing that must be avoided in a street fight. Here are just a few: (1) cocking your arm back prior to punching or striking; (2) tensing your neck, shoulders, or arms prior to striking; (3) widening your eyes or raising your eyebrows; (4) shifting your shoulders; (5) grinning or opening your mouth; and (6) taking a sudden and deep breath.
Punching Power Rule #5: KEEP YOUR WRISTS STRAIGHT. When throwing punching tools (circular or linear), make certain your wrists are correctly aligned with your forearm. If your wrist bends or collapses on impact, you will either sprain or break it.

Remember, a sprained or broken wrist will put you out of commission immediately when fighting.
Punching Power Rule #6: TIGHTEN YOUR FISTS ON IMPACT. Remember to tighten your fists upon impact with your selected target. This action will allow your natural body weapon to travel with optimum speed and efficiency, and it will also augment the impact power of your strike.
Punching Power Rule #7: KNOW HOW TO MAKE A PROPER FIST. It's ironic how some of the most experienced street fighters don't know how to make a proper fist.
Improper fist clenching can be disastrous for some of the following reasons: (1) you can jam, sprain, or break your fingers; (2) you will destroy wrist alignment, resulting in a sprained or broken wrist; or (3) you'll lose significant power when striking.
To make a proper fist, tightly clinch the four fingers evenly in the palm of your hand.
Make certain that your thumb is wrapped securely around your second and third knuckles and flexed down toward the wrist.

Remember that developing
punching power takes time and lots of effort of your part. It won't come over night, but with determination and commitment it can be accomplished:
Onwards. Upwards. Always !
Farai