You start by sitting on the ball and then slowly take your body forward so that your hips are just off the ball and your back is on the ball. Your feet should touch the floor and they should be shoulder width apart. This way you can balance your body with less stress. Keep your hand behind your head to support it.
From this position, you should crunch forward and lift shoulder blades off the ball. When at the top, count one, two three and then slowly lower your shoulder to the starting position. Lie on your back on the floor. Bent your knees up so that feet flat on the floor. Place your arms flat at your sides with your palms up.
Now raise your pelvis and try to bring your knees close to your chest. Be at this position for 1 second and then lower your pelvis to go back to original position. Lie on your back on the floor. Bent your knees up so that feet flat on the floor. Cross your hands to cover your chest. Now crunch up by bringing your head towards your knees, be at that position for 1 second and then slowly lower it till your shoulder blades are just off the floor.