Try laying on your back with your hands either in a triangle beneath the small of your back or above your head wrapped around something heavy like a leg to a sturdy table. Then slowly lift both legs up until they are pointing right at the ceiling. Then sloooowly lower them WITHOUT touching the ground but getting as CLOSE as possible. This works your lower abs. Keep doing those, and do about 20. Always start counting after your abs already hurt, because that way as you get stronger you still improve, so if you do 10 before it starts hurting you are really doing 30.
do regular crunches