Holding the Moon is a traditional posture for most Chinese internal martial arts. If you practice Holding the Moon before you are aware of your shoulder and hip alignment, however, you can reinforce bad posture. Therefore, a good way to learn the posture is lying on the floor.
Lie down on the floor with your feet hip width apart, your arms extended to your sides, and your toes pointing to the ceiling. Pull your feet up by bending your knees until your feet are flat on the floor. Raise your arms up from the sides, bending them at the elbows, until your shoulders start to rise off the floor. Gravity should pull the elbows and hands down so it looks like you are holding a large ball on your chest. Hold this position for up to five minutes.