1. Elongate your core by standing up as straight as possible. This will give you the appearance of a longer torso and a flatter stomach. This is also a great way to decompress your spine and engage your core. Imagine a string attached to your head pulling you up.
2. Suck in your stomach. Not only will this move instantly make your stomach look flatter, but you will also be giving your abs a workout. Your deep core muscles are activated by sucking in your stomach and the longer you suck in, the more toned your core will be. Just remember not to hold your breath while you are sucking in your stomach.
3. Tilt your pelvis back. Tight hip flexor muscles caused by too much sitting can cause your stomach to stick out. This is because when these muscles are contracted they tilt your pelvis forward. In order to flatten your stomach, you want to to tilt your pelvis back. To practice this, lie on the floor and put your hand behind the small of your back. Tilt your pelvis back so that you are squishing your hand into the ground. Hold this for 5 seconds. This is a pelvic tilt. After you have done this lying on the ground, try doing it standing. This little exercise will help bring in your stomach and engage core and pelvic muscles.
4. Back bends. Bending backwards is a great way to stretch tight hip flexors that may be causing your stomach to protrude. Your core muscles really have to engage to prevent you from falling backwards while doing a back bend. This is a great exercise to do every time you get up from sitting. When you are first starting out place your hands behind your hips for added support. As you feel more comfortable with this exercise you can bring your arms overhead while you bend backwards.
5. Side bends. In yoga, this is considered one of the best waist trimming postures. It stretches and tones your abdominal muscles, while at the same time giving your some serious flattening. This great exercise can be done throughout the day.
In addition to the 5 posture fixes, I would recommend regular cardiovascular exercise to help burn belly fat and to decrease bloating. And of course you want to watch what you eat ;)
The video segment should be up in a couple of weeks so you can see how these moves are done!