How to get rid of side stitches?

I’ve recently taken up jogging.
I’m in decently good shape, although I’m not surprised that it’s taking some work to get started.
I’m being careful to breathe right, stretch beforehand, stay hydrated, and warm up.
I’m still getting side stitches, though. What am I forgetting?
Is it just because I’m just getting started? Will it get better?