So many new moms complain to me about their butt after baby. A great exercise to tone the buttocks is the back kick. The added benefit of back kicks is along firming the buttocks it also tones and firms the hamstrings (back of the thigh) and low back. A simple way to learn it is to use a chair for balance.
The exercise: Stand approximately 3 feet away facing the back of a chair. As you hold onto the chair kick your right leg straight back behind you. As you kick back tighten your buttocks. Repeat 15-20 reps then switch sides. Work up to 3 sets on each side.
For more of a challenge don’t use the chair. You’ll incorporate more muscles to keep your balance.