Spring into better abs!
The only way to get better abs is to do crunches, and lots of them! So get on the floor and start doing those cruches to get summer abs. The way you know if your ab muscles are contracting is if you feel a burn in your stomach. It is not comfortable, and is not supposed to be. But when you start to feel the burn, that is when you know your exercise is starting to work. Don't stop your exercise at that point, keep on exercising till you can't exersise any longer. That is when you know you have fully maximized your ab muscles. Stretch!!! And drink plenty of water!