If you have a grown dog, you can still train him or her to walk on a leash. Here's what you can do: While holding the leash firmly, allow your dogs to walk until they have used up the loose leash. In a firm voice, say, "heel." When he pulls, give the "heel" command again and gently pull the leash. Be sure to stand still and firm. This will show your pups that you are in control and that they should listen to you. Once they get this message, they will walk back to your side.