Pulling on leash is a common dog problem and various dog manuals approach it in different ways.
The method that I have had the most success with is quite simple to explain: you and the dog are walking along together when the dog moves out ahead and pulls. You can stop dead in your tracks until the leash is loose. Or you can turn around and go the other way. The dog will follow along (or dash to get ahead of you again!) and then you can reverse yourself again to continue the walk in the original direction. The idea behind this is that the dog will pick up on the idea that in order to go forward a loose leash is required.
If you are using a long retractable leash, walk the dog on a shorter leash (or with the retractable one set for just a few feet) until he is more reliable on leash.
Rewarding the dog when the walking is going well can help too. Have some treats in a pocket and when you and the dog go along nicely for a bit, you can praise and give a treat. You could also click for this behavior or give verbal praise.
In fact, clicking when the dog is walking on a loose leash could quickly get you a dog who walks nicely!
Leash-pulling can be frustrating to deal with. We had a small Basenji who seemed to have the strength of a horse when it came to pulling. It was very embarrassing to walk her in public till we got something of a handle on it. But if you reward even the small successes and keep working on this, you’ll see improvement.
What if These Tips Don’t Work?
You can use a Halti or other halter device, being very careful not to put too much pressure on the dog’s neck. This will give you a physical advantage; then you can use clicker training or other gentle methods for training.
Do note that some dogs don’t like head halters and that they are not meant to be used with sharp tugs which could injure a dog’s neck.. Body harnesses do also exist.
Here are some of these points in a podcast: