This Babyfit article has a good summary of exercises to do and how to do them after you deliver your baby and want to get your abdomen back into shape. First don't begin exercising too early, as this can cause more harm than good. Check with your doctor to see when you are able to begin exercising. Second, get back into things gradually. There are some exercises listed though that are recommened for within 24 hours after delivery, so it is worth checking out ahead of time.