HOW: Get set up near a wall or an object such as a chair to ensure safety if you were to lose your balance. Slowly shift your weight laterally all the way to one side trying to put 100% of your weight onto one leg, then shift your weight towards the opposite side, repeat.
FEEL: This should feel like you're transferring your weight from one leg to the other. If anything, you should feel your calf, quad, and the outside of your hip muscles working with this exercise.
COMPENSATION: Be sure not to compensate at your hips or trunk and lean over side-to-side. Try to keep your body nice and tall in a straight line