Lie on your back on the floor with your knees bent and feet flat. Have your elbows out and your hands behind the base of your head.
Raise your head, shoulders and upper back and legs off the floor, contracting your abs, so that you are bringing your head towards your knees.
Then lower your upper body and legs back down again so that your feet are nearly touching the floor. Then repeat the exercise.
Do not drag your head and neck upwards with your hands. Focus on using your upper body to raise you up.