Triceps work is important not only for the overall upper hand strength and size but also for proportion. People tend to work the biceps far more than the triceps which creates a very odd appearance in the arm.
One such exercise which is very good at developing the triceps is the triceps kickback. Here is how to perform this exercise:
Holding a dumbbell in one hand with the palm facing inwards, bend forward at the hip and place your other hand on a bench to steady yourself.
To balance you place one of your feet in front of the other. Normally the foot on the side of the dumbbell is the one placed forward.
Keeping in this bent over position bend your elbow raising your upper arm parallel with the floor and your torso. Finally straighten your elbow out effectively kicking the dumbbell back and upwards. Slowly reverse the movement and repeat for repetitions.
While doing this keep your elbow tucked into your sides.