Lying on the floor, flat on your back with your knees bent, place your feet on a chair or resting on a bench or on exercise ball. Your neck and head should be relaxed with your hands at the sides of your head.
Concentrate on tensing and contracting the abs muscles holding the contraction throughout the movement. At the top try to contract your abdominals intensely.
Again, try to maintain tension in your abs and focus on slow controlled movements.
As with all abs exercises of this type keep your lower back flat on the ground. Do not lift your lower back off the ground and actually sit up at any time. This uses more hip flexors than abdominals.