Get on all fours to start and make sure your hips are stacked over your knees and shoulders over your wrists.
Lift your leg off the floor, and while keeping your knee bent and foot flexed, start to pulse your leg up. Imagine you're tapping the ceiling with your heel and remember to squeeze your glutes as you do it.
For the next variation keep your posture the same, but this time lift your leg out to the side and start to pulse your leg behind you. Keep your knee level with your body to get as much work out of your glutes.