A great exercise to wake up your gluts (and to help them look better) is the glut bridge.
Perform this by lying on your back with your legs bent and feet hip width on the ground. Arms are at your side with your palms facing up. With your feet flat on the ground, push your hips up off the ground. Try to maintain neutral spine, and avoid arching your back. It may be helpful to hold a ball (medicine, basketball or beach wall) between your knees.
Hold for a few seconds and then slowly lower. Try to relax your hamstrings to keep most of the work in the gluts. Repeat up to twelve times.
You can advance this move (but only when you can do it in perfect form), by bending one leg in the air, and pushing into the leg that is on the ground.