Spine: Stand with your back to the wall. Your shoulder blades and backside must touch it, with your mid-back slightly away. Hold this shape at all times.
Many people who spend hours sitting lack proper glute activation. Tense your glutes as you walk to improve the posture of your whole body.
Chest: Take a deep breath to expand your chest. Now breathe normally, but keep your chest up. This draws in your belly and enhances your physique.
Abs: Six-pack or not, tensing your abs as often as possible will work them and improve their shape. For instance, you could do it while carrying especially heavy objects, or - if nothing else works - climbing the stairs.
From Men's Health