The Cook Hip Lift
Most people have trouble with glute activation. Glutes are pretty much the most important muscle in the body for functional movement (and hotness), so training those butt muscles to fire is an extremely important part of any training routine. Cook Hip Lifts, which I stole from Gray Cook, force you to pivot at your hip and use your glute max to bridge while preventing you from compensating with your lower back. Do 12 of these on each leg early in a workout and at least twice a week.