Read something about exercise and muscle cramps just yesterday. If it's a side stitch you're concerned about, eating only a light meal at least two hours ahead of exercising will help. Gently stretching first helps so you'll be less likely to tear muscle tissue. Stretching after helps the muscle to process a build-up of lactic acid before it gets to be a problem.
Yes it matters, you can cause physical pain and lasting damage to the muscles if you do not stretch thoroughly, and properly. As far as getting cramps goes, eat foods high in potassium. Such as, bananas, salmon, avocados, raisins, carrots, baked and sweet potatoes with skin, and dried apricots. They will help your body prevent cramps.