Most people hold their pulling dogs on a short leash because the second they release the leash the dog takes off. But if you do this the dog never learns to stay close to you on a loose leash . The natural reaction to tension on the leash is called the oppositional reflex- your dog will resist presssure and pull.The classic way to teach loose leash walking is to stop walking when your dog pulls or to turn and go in the other direction , wait for your dog to catch up and then turn back and walk on again. This is ultimately effective but can be slow and tedious .
The easiest quickest way to teach your dog to walk on a loose leash is to use a long line !
With your dog on a long line reward well and frequently when your dog is close to you walking with you ,and when it goes away from you you move in the opposite direction and call it . In a short time your dog is stuck to you like glue on a loose leash! You are unpredictable so your dog needs to focus on you ,and being beside you is rewarding . Plus there is no pressure on the leash to resist .
Another way to teach this is to teach your dog to focus on your hand or your face (hold a treat for your dog to watch and lower it to your dog , or start with it low and raise it to your eyes, then give it to your dog , or put your hand to your dog and reward , or count to 3 and drop treats beside you on 3. Or simply hand treats to your dog when it's beside you . Any of these keep your dog beside you .
Just rewarding your dog when it's beside you- even when you are sitting down watching the tv, working on the computer ( or even just scrolling! ), talking on the phone , eating etc - builds positive associations with being beside you .Then when walking, your dog WANTS to be beside you .