Take 10 minutes to stretch out your entire body. This warm up is absolutely necessary in order to avoid injury. Remember not to bounce around during stretches and don't overexert your body for the purposes of stretching further.
Put on a pair of soft knee pads, such as the kind that are used for volleyball. Although the dancers on SYTYCD don't wear them, you'll need them until you learn to master the move without slamming your knees into the floor. Shoes are optional.
Stand with your feet shoulder width apart and then bend at the knees. You should bend down to a squatting position, but not so low as if you are sitting in a chair.
Shift your body weight forward so that you're balancing on your toes. Then step your right leg forward into a lunge, so that the left knee grazes the floor beneath you. In the next instant, use your arms to catch you as you lie down in a planking position and then fall to the floor. All together, the move should take one to two seconds to perform so keep practicing until you've mastered it. When you're ready, perform it without knee pads or conceal the knee pads beneath long pads if they help.