The principle of opposing movements of the hands and legs: In the rotating motion, you can keep your body in balance without falling down when your hands and legs are moving in different directions. You can experience this principle of yin/yang when you try to rotate your body while sitting on a swivel chair. You can apply this principle to your form by  imagining you were sitting on a swivel chair. For example, you can do the last sequence of the Body and Mind Method, "Return Chi to One", with this visual.
Master Luke Chan demonstrates body rotation on a swivel chair