Stiff leg deadlifts is the most effective exercise for the hamstrings. The primary muscles used in the exercises are the hamstring, glutes and lower back. Secondary muscles used are the arms, traps, shoulders and upper back.
To perform stiff leg deadlifts grip the barbell a little wider than shoulder width. Bend at the waist and lower the bar to the top of your feet. Keep the bar as close to your legs as possible throughout the entire movement. Your knees should be slightly bent and not locked out. Raise the bar back to the starting position in a controlled manner and repeat.
At the top of the movement do not lock out your back, raise the weight just before you are fully upright and then go down again. This will place less pressure on your lower back and will also keep the tension on your hamstrings.