HOW: Get set-up on the ground supporting yourself with your arms and with your knees bent. Let both knees fall to one side by moving through hip rotation range of motion. Go through the full range of motion that you feel comfortable with, then move both knees in the opposite direction. Repeat.
FEEL: You should feel movement primarily at your hips as well as your pelvis and low back at the end-ranges. Try to control the motion with your core muscles.
COMPENSATION: Do not allow excessive and early pelvis and low back movement.