This always use to happen to me when I mouth breathed during running. Are you a mouth breather? Now, I breath in through my nose, out through the mouth..no side stitches. I hope this helps.

A common cause of a side stitch is shallow breathing. It happens pretty often to new runners, or runners increasing their pace, when we start breathing faster and harder than we're used to. The trick is to focus on filling your belly (your diaphragm, really), not your chest, with air, and breathe out deeply. A quick fix when you get a stitch is to breathe out REALLY HARD. If I get a stitch, I pause, take in a deep breath bending over at the waist so I can feel my diaphragm filling, and then give a big hefty blow out. Imaging you're a bellows or are blowing out candles.

If you're not sure how to breathe from your diaphragm, lay on the floor, put a heavy book on your belly, and practice taking in deep breaths the move the book up and down. It is awkward at first but once you figure out how to "fill your diaphragm" rather than "fill your lungs" it makes sense. It's the same intake of breath as when you sigh.

If you've ever been a singer in a church choir, or sung opera or chamber or some other kind on non-amplified music, breathing for running is the same as breathing for singing. Fill the belly deeply and let the air out completely. Good luck!

I've found that timing is everything. Generally landing on exhale on what would be the opposite side the stitch tends to occur helped me early on. It becomes second nature after a while. Watch what you eat and portion size within a couple of hours of the run. On a side note, I've experienced a recurrence of side cramps with worn or otherwise improper shoe selection. For instance, I am a neutral runner and Brooks either offers the Glycerin or the Ghost. I get cramps with the Ghost but it's smooth sailing with the Glycerin. That said, footbed padding may be an issue.