HOW: Get set-up in front of a wall or an object to use for balance. While keeping your glutes and quads tight to keep your knees straight, lift your heels off the ground in a slow and controlled manner. Then shift all your weight over to one leg, do not lose any heel height. Hold this position for the desired amount of time. Really drive the balls of your foot into the ground.
FEEL: You should feel your calf getting a workout, but also your glutes and quads working as well to help keep your legs straight.
COMPENSATION: Do not let your knee bend as that is a different exercise. Try not to lower your heel as your shift weight over to one side. This is not a balance exercise, so hold onto something to help with balance as the goal of this exercise is to strengthen your calves!