Begin starting with your feet hip width apart and then take a long step straight forward. Bending with both knees, lower your body until your back knee is within one inch of the ground. Pause and hold for 2 seconds, then raise your self back up. Repeat while keeping your back perfectly straight and concentrating on using those glutes and hamstrings to push yourself back up. Note: while you are in the down position, check to make sure your shin of the front leg is perpendicular to the ground. Try taking longer strides if your knee of the front leg is coming out over the toes.
Tip: Doing this exercise correctly is extremely important for the health of your knee. The front knee should also be tracking over the front foot, do not allow it to fall in or out. To increase resistance try holding dumbbells in each hand.