To start, the moonwalk is all about the illusion of where your body weight is placed. Typically when a person walks, their full weight is placed on the foot when it is completely flat on the ground. The foot that is slightly lifted up on the ball of the foot does not hold the full weight of the body. In the moonwalk, this principle is reversed.
You will need to get used to the shift of body weight before you can truely master the moonwalk. Start by standing with your feet about shoulder-width apart. Pick up the heal of your right foot while keeping the ball of your foot on the ground. Without putting your heel down, shift your full weight to your right foot. While you shift that weight, keep your left foot flat to the ground and drag it backwards. Practice this move a couple times until it feels comfortable.
You have just learned the beginning of the moonwalk. To continue moonwalking, you will need to alter that movement from foot to foot. Start by doing your first step. Then when your left foot is behind your right foot, lift the heal of your left foot and shift your weight to that foot. Simultaneously lower your right heal and drag your right foot along the floor. Repeat these movements until you are completely comfortable.
Once you are comfortable, you have mastered the basic moonwalk. You can add some head bops, arm movements or maybe a spin at the end to add some personality. Remember dancing is about having fun and not taking yourself too seriously. Enjoy!