Here's how to do the one-leg deadlift:
Start in a standing position either on the floor or on a step with your desired weight in each hand (15 lbs shown here). Lift one leg and slowly bend your torso forward as you lift your leg behind you.
Contine this movement until your body resembles a "T". Then slowly return to starting position. You should feel this working your hamstrings but it is also a great stability exercise if done as shown on one leg. I find setting-up in front of a mirror helps tremendously with my balance. If you don't have a mirror, try to concentrate your sight on an immobile object. Also, try to keep your standing leg straight without completely locking your knee. I usually do 8 reps on one leg, then switch to the other leg and so forth.
Start in a standing position either on the floor or on a step with your desired weight in each hand (15 lbs shown here). Lift one leg and slowly bend your torso forward as you lift your leg behind you.
Modifications:
To make this move easier, try a standard two-leg deadlift. Your torso will move in the same manner while both of your legs will stand straight.
To increase the intensity, try using heavier weights, adding more risers under your step, or doing these while standing on a bosu ball.
