Roll the vial of insulin back and fourth in your palm before you put it in the syringe. Do the same thing if the insulin is already in the syringe. Pinch the skin of the injection site slightly and target the syringe at either a 45 or 90 degree to make sure that the insulin is injected under the fatty layer of the skin. Rotate the injection sites. Choose the next site at least an inch away from your earlier site.