I agree...deep, controlled, regular breathing while you run will help.
Also you can try some of these tips to reduce or prevent side stitches and other cramps:
---Walk for a couple of minutes before you run. Once you are warm, stretch out your sides before you start running.
---Make sure you are well-hydrated before you run.
---You definitely don't want to eat or drink too much right before running, but you may want to load up on some potassium a couple of hours in advance. Bananas and raisins are both good natural sources of potassium.