HOW: Get set-up near a wall, while standing on one leg (further away from the wall), hold a ball against the wall with the outside of your thigh/knee on the side that is closer to the wall. While maintaining this, let your hip/pelvis sink on the side further away from the wall followed by lifting your hip back up to push harder into the wall. Repeat
FEEL: You will feel your hip muscles on both sides working, especially the one that is performing hip drop/hikes. You may also feel your quads and calves working.
COMPENSATION: Do not drop the ball, try to keep your knee relatively straight on the side that is on the ground. Try to maintain a lean towards the wall.