Mass Transfer. Straightening the rear leg and lowering the hips at the moment of impact adds body mass to the strike. Drop vertically or at a forward oblique, keep the body erect, do not lean. Mass transfer requires the moment of impact of a punch to be simultaneous with the planting of the stepping foot. Holding the center of mass slightly higher in anticipation of executing an attack will allow you to transfer more mass into the attack. Holding the center of mass slightly lower in anticipation of receiving an attack will allow you to brace yourself against the attacking force.
Hand Twist. Punches and many other hand techniques use hand twist. As the technique is executed, the hand rotates and "snaps" into the impact. The retracting hand untwists and is reset so it may then twist into another technique. When punching, align the elbow, arm, and shoulder behind the fist so they transfer all their power to the fist. The twist occurs a split second before impact so that maximum force is transferred to the opponent.
Extraneous Movement. When a fist or foot moves directly at an opponent, it is difficult for the opponent to detect the movement. The eye perceives the fist as getting larger as it gets closer, but there are few other visual cues to alert the opponent of its movement. It the fist swings out to the side, as in a hook, it may alert the opponent to the attack.
Linear/Circular Motion. Power may be applied in a linear or a circular motion. A punch may be executed as a straight jab or as a hook. Each generates power in a different way. The jab has the mass of the body directly behind it and it may be executed quickly, but it only has a short distance in which to generate its power. The hook has the twisting force of the body and hips behind it and has a greater distance over which to generate its power, but since it moves over a greater distance, it is slower than the jab. The choice between a linear attack and a circular attack depends on the situation, the opponent (skill, size, quickness, etc.), and on you (skill, size, quickness, etc.).