Your feet should be together when you begin, with your left foot popped up slightly so that you are balancing on the ball of your foot. Most of your weight should be supported by your right foot. Keep your right foot in the same place, and step out to the left, just past the width of your shoulders. As you step to the left, let your hips follow your foot. Your left hip should be popped out slightly to the left side, just over your left foot. Once your left foot is popped out, lightly slide your right foot across the floor to meet your left foot. Then slide your right foot behind you. As you slide your right foot back, lift your left foot up slightly. Once your right foot is in place behind you, rock forward so that your weight shifts from your right foot to your left foot. Then bring your right foot up to meet it. This is the main starting position for the cha cha.

Summary:
Start with your feet together. Step out to the left. Slide your right foot to meet your left and then back. Rock forward to your left foot.