Treats. I taught Ginger not to pull by giving her a small treat on occasion. Initially, I think I would say her name. she would look at me, I would treat her. Just at various times during the walk. Then after a few days rather than calling her I would treat and praise her if she would just look at me during the walk. She soon learned that she didn't want to be too far from my left hand, and if she paid attention to me during the walk she would get a treat, or praise, or some other positive reinforcement. She forgot all about pulling. Now that is how I trained my dog. But, let me warn you, Ginger isn't the perfect little walker. She doesn't pull, but she doesn't walk at heel by my side. She is allowed to explore and sniff.