Don't know squat? You should. Squats are a perfect exercise for your buttocks and thigh muscles.
If you are a squat newbie, squat with either no weights or while holding very light dumbbells. You can increase the weight of the dumbbells, or even add dumbbells to your routine, as you get used to doing squats over time. If you squat with a weight behind your shoulders, be sure you've got a spotter. The more weight you add, the stronger your squats -- and your legs, thighs, and buttocks -- will be.