I get a stitch while running now and again, and one way I've found to stop them is by changing my breathing pattern compared to my pacing.
e.g. If I am say taking 1 breath in for every 4 paces and 1 breath out for 4 paces and I develop a stitch, I will then maybe take one breath in for 3 paces and 1 breath out for 4 paces, and keep varying my breathing in different ways like this.
This works for me every time. works for me.