1. Lie on your back, knees bent, feet flat on the floor. Place the ball between your hands and knees. Keep your arms straight.
2. Begin by first moving the ball back and forth gently between your hands and knees. Keep your spine long, and your skull on the floor without arching your neck or lower back. This placement activates your core.
3. Raise your head, neck, and shoulders off the floor, without pressing too hard with your hands. The spine should remain stable on the ground, without arching. Keep your tail bone firmly on the floor. Repeat this 8-10 times.
From 101 Ways to Work Out On the Ball
By Elizabeth Gillies - a good book I recommend.