HOW: Start first by balancing on one leg. Once you feel you are balanced, slowly bring your other leg behind you and move it left and right. As you move your leg, you'll notice that balancing is harder! The faster and the greater distance you move your leg, the harder the exercise will be.
FEEL: You should feel all the muscles in your foot and glutes working to keep you stable.
COMPENSATION: Do not let your hip drop and "sit" into your hip. You should actively be squeezing your glutes the entire time.