Most dogs can get the point of loose leash walking pretty easily, but I see very few who can walk in a strict heel position for any period of time. Often times, when teaching your dog to heal, they start to 'yo-yo', where they will walk with you for a few steps, pull forward, fall back and walk with you, pull forward etc. All of my dogs still do this occasionally, and one of them is particularly bad at it. This video, made by a dog trainer whom I really enjoy watching and who I think has great techniques, shows you how you can actively stop your dog from this annoying walking behavior. This video is worth more than a thousand words. As usual with dog training it is way more helpful to watch what must be done rather than read it.One thing I would add to the video is that if you are using a prong (which you shouldn't need to with correct techniques) or a regular collar, you can quickly and lightly correct your dog with a firm yet quick tug on the leash the moment you dog begins to rush forward. If you are being very interactive with you dog, like in the video, you shouldn't need to do this, but if you are out for an everyday walk and your dog starts to 'yo-yo' don't hesitate to give a quick correcting, and then start using the techniques in the video if he continues to pull ahead.