Does sucking in your stomach while doing cardio make a difference?

If I do cardio for an hour, would sucking in my stomach for that time make a difference to my belly fat? Also, how do you know if you are sucking it in the right way (if there is such a thing LoL).

Pulling your abs in and up will definitely help strengthen your abs but it's not going to do anything to get rid of fat. You're talking about two things here: fat and muscle strength. You can spot tone, but you can't ever spot lose.

That being said, strengthening your abs is always a great idea. And once you lose the fat (through diet and exercise, interval cardio is most effective) you'll see a big difference in your abs.

To feel what it should feel like, cough and feel how your abdomen pulls in, as if you have on a girdle. Your abs, starting down at the pelvic floor (imagine pulling up and giving support to your womanly parts) and going up to your lower rib cage, should pull in AND up. Exhale, using the breathe to move air out of your abdomen and pull the abs in as tight as possible--imagine your waist getting smaller. Remember that feeling. Just "sucking in" isn't going to activate your abs.

If you are walking uphill, for example, on a treadmill or outside, you should pull your abs up and in and imagine that the movement of your legs is coming from your abs. Use your abs to power you up a hill. If you're on a bike, use your abs to pull your legs up-as if there is a string connecting your quads to your abs.

Good luck!

In pilates they say that it should feel like you are trying to have your abs touch your spine or like there is a string attached to the inside of your Abs pulling them toward your spine.

Good luck!

Well by sucking in your belly you will be breathing less, with hat being said you will burn less cal's because you require oxygen to burn calories!

It's an issue of proper posture and form, part of which entails holding your abdominal muscles in a certain way. When you have good form, you can perform exercises more effectively and you are less likely to injure yourself.