step number one to get janet jackson's abs: ask her for them. if that's not possible, make sure you have her genetics.
if you just want to optimize your own abs, then like mentioned, do lots of cardio to reduce bodyfat. if you're female, you need to go below approximately 14%.
you should also do a good
weight routine for your abs no more than twice a week to build up the muscle.
a thousand situps is crap - situps are crap anyway: they work your
hip flexors through much of the movement and don't specifically target your abs. do three sets of 25 crunches twice a week while holding a weight on your chest and you'll see results a lot faster.