Activate your core and posterior chain (a fancy term for the backside of your body) with a bridge. This is a great exercise to use as a warmup.
Directions:
Lie on your back with your knees bent, feet flat on the floor, and your arms extended by your sides.
Pushing through your feet and bracing your core, raise your bottom off the ground until your hips are fully extended, squeezing your glutes at the top.
Slowly return to the starting position and repeat.