Start in the forward stance with your front hand extended. Without moving your upper body or front foot, quickly step forward with your rear foot into the front stance. Be sure to stay down throughout the action, and draw your legs together as you go forward. Punch at the very last instant of the step. Your body, back leg, and punch should all lock at the same time.
Reverse Punch (Gyaku Zuki)
Start in the forward stance with your front hand extended. Turn the hips forward, breath out, and punch simultaneously.