Step 1: Sit on the floor with your knees bent and your feet flat on the floor. Place your hands behind your head. Your elbows should be pointing outward.
Step 2: Raise your head, shoulders and upper body toward your knees. Avoid arching your back. Lead with your chest, not your head. Exhale as you rise, inhale as you lower back down to the mat.
Modification (Beginner): Do not sit all the way up. Instead, do small crunches by lifting only your upper back and shoulders off the ground.