We learned this exercise from a kung fu instructor.

Choose a partner to learn with. Stand facing each other, but not necessarily directly across from each other. Put up your right forearms (can also use left) in a “block” stance and make contact. Bend at the knees and let your feet be deeply rooted into the ground. Let your back straighten and your tailbone drop down. Relax. Breathe. Close your eyes.

Now feel your opponent's balance by pushing with your forearm. He will also feel out your balance. Without force, using your balance, try to upset his balance. Keep your feet rooted and bend from the knees, hips, waist, and shoulders. Continually try to relax yourself and focus on your balance and his. When you or he step away to maintain balance, the match is up and you can start over.