No. 1: Improve Your Posture
Slouch and your stomach pooches. So straighten up, and you've done your abs a favor without breaking a sweat! For better posture while standing, align your ears over your shoulders, shoulders over hips, hips over knees, and knees over ankles. Keep the fronts of the shoulders open like a shirt on a hanger, instead of a shirt on a peg. Draw your navel to your spine and keep your weight even on the balls of your feet and your heels.
No. 2: Think Whole-Body Exercise
Don't get so into your abs that you overlook your other muscles. Your core muscles also include your glutes and back muscles, for instance. Pilates is one way to work all of the core muscles, plus the arms and legs, for a whole-body workout that does strengthens the abs -- and more.