Strengthen Your Legs
Your power comes from the ground up. The way that you both kick and punch requires the movement of your legs and thus by strengthening them you strengthen the power that you can generate with your body. Your legs are the foundation of every movement you make. There are numerous ways to strengthen them with both aerobic and anaerobic exercise. Activities such as running and punching and hopping kicks will improve the endurance of your legs through aerobic exercise. While exercises such as squat and kick and power kicking will build your anaerobic strength. This anaerobic exercise will provide explosive power to your muscles and thus allow you to deliver formidable strikes with both your kicks and punches.
Upper Body Rotation
All of your strikes require the rotation of your body, from punches to head kicks. Your entire upper body can create the torque needed to produce severe strikes. As such it is important to work on your upper body rotation in order to be better equipped for advanced and powerful striking. You can improve on this by making sure your shoulder is in front of your chin as you punch then snap the punch back to its original position in fighting stance.
Mastering martial arts requires building and nourishing numerous attributes, flexibility, speed, balance, distance and timing are all major elements.
Speed will always beat power; technique can beat speed and power, but it is a potent mix if you have all three!