Crunches, or sit-ups, tone the upper abs. To Tone the lower ones, lay on your back like you are going to do a sit up. raise your legs off the ground and like and bend them. its kinda hard to explain..your knees should be close to your face. put your hands behind your head and do crunches like that. that focuses on the lower abs rather than the upper ones. standing up straight and touching your toes also works the lower abs. good luck!
Little Gibby