You might live in an area that is not a good environment for leash training your puppy.
It might be a crowded apartment complex, where it is too noisy and there are far too many distractions.
But then your puppy morphs into adulthood, and you and Fido move to a more spacious area where there are trails that you can take him for scenic walks.
The problem is that he hasn't been leash trained.
Virtually all areas have ordinances that a dog must be on a leash when they are outside with their owners.
But there's no need to panic because it's possible to train an adult dog, no matter what their age to walk on a leash.
First, you need to have a pocket full of your dog's favorite treats before you head out so that you can reward him or her when they are walking on the leash properly.
The idea when walking a dog is that they should stay by your side with the leash loose, so that they are not tugging.
In addition, when you first put your dog on the leash, he may go wild and begin tugging on the leash, if so, stop, turn around and walk the other way.
When he doesn't pull on the leash, praise and give him a yummy treat as a reward.
You may have a dog that truly wants to pull and if so, you might want to begin using a harness, which goes over the dogs body so that if he pulls he is not capable of hurting himself like he can on a tradition collar.
As your dog becomes more accustomed to the leash and no longer pulls, you can always switch them to a traditional collar and leash.
The idea to stopping any pulling is that when it happens you immediately switch directions, when you do this the dog learns that by pulling he is not getting anywhere fast.
The more you work with your dog on a daily basis with the leash training, the easier it will become until he or she is walking on the leash loosely and you can then take your dog anywhere you please knowing he isn't going to drag you down the street, which is not only frustrating but it is embarrassing as well because it shows others that your dog is truly the leader and you are the follower, which is totally a reversal of roles.
Therefore, every day, for several minutes, put the leash on your dog and head out, when the dog pulls, stop the direction you are going and turn and walk in the opposite direction.
You may find you are turning the direction every few seconds when you first begin the training but that is okay, your dog will understand what it is you want from him with patience, persistence, and consistency, meaning you walk your dog daily, because the more you expose him to the activity, the faster you can train him not to pull.