Dogs pull because pulling works. The dog wants to get to the tree, pulls, and arrives at the tree. That is the entire behaviour, reinforced several hundred times before anyone decides it is a problem.
Which is also the way out. If pulling stops producing forward progress, and slack leash reliably does, the dog changes what it does. That takes longer than a weekend and it is mostly about your consistency rather than the dog's intelligence.
Before you start
Get the equipment sorted first, because you cannot train through a harness that is hurting the dog or a leash you cannot hold.
Use a well-fitted harness rather than attaching the leash to a flat collar. A dog that lunges into a collar takes the force through its throat. A leash of about six feet gives you enough room to reward slack without giving away so much that the dog is at speed before you react. Retractable leads teach the opposite of what you want here: they reward pulling with more length, continuously.
Stop and wait
The core method, and the least complicated.
The moment the leash goes tight, stop walking. Do not pull back, do not tell the dog off, do not reel them in. Just stop, and become extremely boring.
Wait. The dog will eventually ease the tension — turn to look at you, step back, sit. The instant there is slack, say something consistent and cheerful and walk on. Forward motion is the reward, and it is the one the dog actually wants.
Expect the first few sessions to cover almost no ground. That is the method working, not failing. You may spend ten minutes on a driveway. The dog is learning that tension stops the world.
Direction changes
Useful for dogs that treat stopping as a chance to sniff and reset.
When the leash tightens, turn and walk the other way without a word. The dog now has to pay attention to where you are going, because you have stopped being predictable. Turn as often as needed. It looks ridiculous and it works.
The point is not to jerk the dog around — turn smoothly and let them catch up. The lesson is that you set the direction.
Reward the loose leash
The part people skip, and the part that does most of the work.
Most of the walk, your dog is probably not pulling. If the only thing that gets a reaction from you is pulling, you have taught the dog that tension is how to get your attention.
So mark and reward the good position while it is happening. Treats early on, then intermittently, then mostly praise. You are building a picture of where the dog gets paid for walking, and it needs to be more interesting than the alternative.
Everyone has to do the same thing
This matters more than which technique you choose.
If you stop dead every time the leash tightens and someone else in the house lets the dog tow them to the park because they are in a hurry, the dog has not learned that pulling fails. It has learned that pulling fails sometimes, which is a slot machine. Intermittent reward is the most durable reinforcement there is, and you have accidentally built one.
Agree the rule with everyone who walks the dog, including the dog walker, before you start. A household that half-does this for six months makes less progress than one that fully does it for three weeks.
Where gear fits
Honestly: gear is management, not a solution.
A front-clip or dual-clip harness redirects a pulling dog sideways so pulling stops producing forward progress — which happens to be exactly the lesson you are trying to teach, so it works with the training rather than against it. A bungee lead absorbs the shock when a dog hits the end, which spares your shoulder and the dog's chest during the weeks it takes to get there.
Both make the training possible by making the walks survivable. Neither one teaches anything on its own. A dog in a front-clip harness that is never trained is a dog that pulls slightly less, indefinitely.
Head halters and other no-pull tools sit in the same category. They can give a handler control over a dog that badly outweighs them, and that is a legitimate reason to use one. They are still not a substitute for teaching the behaviour, and a dog that has only ever been managed will pull the moment the tool comes off.
What this article will not fix
Ordinary pulling is a training problem. Lunging, barking or fixating on other dogs, people, cars or wildlife is usually not — that is a reactivity or fear problem wearing a pulling costume, and the methods above will not touch it. It needs a qualified trainer or behaviourist who can see the dog.
Same for a dog whose pulling changed suddenly, or who resists the harness where they did not before. Check for pain first.
If you are starting out, a front-clip or dual-clip harness and a bungee lead will make the first month considerably easier. Both are in Tactical & Trail, and the Field Guide covers fit and clip positions in more detail.