Most of the time, simply stopping has NOT worked for me. What works better is to change directions with no warning when he gets in front of you (and before he hits the end of the leash...try to prevent the leash getting tight. Remember it takes TWO to make the leash tight). Make a u-turn or even just a 90 degree turn and keep going. Don't give him any indication that you're about to turn, just do it. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. And repeat.And repeat. And repeat. And repeat. And repeat. And repeat. And repeat. Eventually it'll get there.