Many puppies pull when they are walked on a leash, and if your dog is going to be a large breed dog, this can be bad news for you. They want to get where they are going, and they want to get their now. But with leash training, you begin by teaching your puppy to walk on a loose leash and stay where you want them. Your job in this situation is to teach them what you expect them to do when they are on a leash and what you do not expect them to do on a leash.
Step 1: Get your puppy used to wearing a collar. Slip it on his neck while he is eating, or sleeping. Having a distraction for him while you are trying to put something new on him makes it easier. His first reaction is going to be to try to get it off, or try to make you feel bad for him. He may whine, roll around and try to scratch it off, or pretend it hurts. Remember, this is something foreign to him. No matter how bad you feel about it, do not take it off until he leaves it alone. Put it on and take it off every day for a week. That way he sees that you are not going to hurt him with it and that it really doesn’t bother him at all.
Step 2: Once he is able to wear his collar without incident, it is time to move onto the leash. The first part in this step is to show him the leash. Let him know it is noting to be feared. I don’t recommend a fancy leash for this part, because he will more than likely chew on it. During this step, supervise your puppy. Clip the leash onto his collar and let him sniff, lick, and drag it around. Do this a few times a day until your puppy is used to it.
Step 3: When your puppy is comfortable with the leash being on him, it is time to hold the other end of the leash. If your dog is a puppy or likes to follow you around the house, you already have an advantage. Make the first few leash sessions short. Continue until the dog is comfortable trotting along at your side with the leash still loose. If your puppy begins to walk ahead of you, or pull on the leash, stop walking. If you continue walking, it will make him think it is okay to pull you. After you stop walking, call him back to you and reward him for returning. Never jerk on his leash because this might hurt him or make him back track on training.
Once he is back at your side and rewarded for returning, continue walking.
This works for puppies. See my article on leash training dogs for any dog over 6 months old.