If you're working your abs hard enough, you shouldn't be able to work them every day
For me, 2-3 times a week is good for abs.
They need to be a little sore after a workout, as you are tearing a certain amount of muscle fibers to rebuild stronger. Be sure you are using resistance, rather than just pumping out crunches until you pass out. You can use the
crunch machine at the gym, or do a
kneeling crunch (that is my favourite exercise to do, period!! feels sooooooooo good). For obliques,
side bends are great. -----click on those exercise names to see them-----
Just work them like any other muscle - say 3 sets of 8-10 reps, with enough weight so that it is very difficult to finish the last few reps of the 3rd set.