What is the key to get a completely flat stomach?

I am thin but there is just flab on my belly (mostly lower belly). How can I get a flat stomach like this:

http://farm4.static.flickr.com/3040/3035424441_0e1e882c5f.jpg

or

http://www.candyapplemag.com/images/beauty/mar08/BEAUTY-FLAT-STOMACH.jpg

Eating? Jogging? How much? What else? Thanks!