Shapely, strong hamstrings round out the back of your legs. Make sure you do at least two exercises per leg day that are strictly for your hamstrings.
Find the hamstring curl machine.
Lie face-down on the bench portion. The leg pad of the machine should touch the back of your legs close to the bottom of your calves.
Grasp the handles, and bend your knees to bring your heels toward your butt. Contract your hamstrings, and bring the leg pad as close to your butt as possible. Hold for a one-two count at the top of the movement.
Slowly lower the leg pad back to starting position.