1. Sit up tall
  2. Place the soles of your feet together
  3. Let your knees drop out to the side
  4. Gently shuffle your feet toward your groin
  5. You should feel the inside of your thighs stretch
  6. Hold 20-30 seconds
  7. Repeat 5 times.

This can also be done as a more gentle stretch in a supine or lying down position; bring the soles of the feet together in much the same way and slowly let the weight of the knees take them closer to the ground.

This is also a great stretch for anyone with stiff hips.