Fat on the back of the arms can make some girls self conscious about their appearance. To work your triceps, try dips. Sit on the edge of a chair and place your hands on the chair, directly next to your hips. Wrap your fingers around the edge of the chair, straighten your back and tighten your abdominal muscles. Tuck your elbows by your sides and walk your feet forward 24 inches. Lift your hips off the chair. Lower your hips toward the floor, bending your elbows as you lower. Keep your elbows tucked as you descend. Stop when the back of your arms are parallel to the floor, push your arms to straight, lifting your hips in front of the chair. Complete 12 to 15 reps, stopping when your triceps fatigue.