Pulling is not stubbornness or a dominance thing. It is a habit the dog learned because it works: every time the lead goes tight and you follow, the dog gets closer to the lamp post, the park gate or the other dog. Dogs also naturally walk faster than we do, so a slow human-paced stroll is hard work for them. Animal-welfare groups such as the RSPCA and Blue Cross describe the same idea: the way to change it is to teach that a loose lead is the fastest way to get where they want to go.
Tell us about your dog and the walk, and the tool gives you a short plan with a treat rhythm to start with.
Pulling stops working, loose lead starts working. That is the whole trick.
Do not use choke chains, prong collars, shock collars or harsh lead corrections. Welfare groups including the RSPCA advise against them because they can hurt and frighten the dog and do not teach what to do instead. Retractable leads are also tricky for training because they keep a little tension on all the time, which teaches pulling. A normal lead of about 1.5–2 metres is easier to work with. A well-fitted harness or flat collar is fine; a headcollar can help strong dogs but must be introduced slowly and gently, and is a tool rather than a fix.
If your dog suddenly starts pulling much more, coughs or gags on the lead, seems sore, or you are worried about fear or aggression around other dogs, ask your vet first and then a qualified reward-based trainer or behaviourist. Pain and anxiety can look like "bad walking". If you are looking for a new dog, start with a local shelter or rescue; many of them offer free training advice after adoption.