Your dog walks a reasonable line down the street. Then a dog comes around the corner and the leash goes tight as a wire. Twenty seconds later you have your dog back.
This is worth separating from ordinary pulling. A dog who tows you the whole walk has learned that leaning forward works. A dog who is fine until another dog appears has a specific trigger, and the trigger is what you train.
What the pulling is actually about
For most adolescent dogs it is wanting to get there. Other dogs are the most interesting thing on the street, and your dog has spent months being allowed to reach them. For some dogs it is the opposite and the pulling is a way of getting away.
Both look the same on the end of a leash. You can tell them apart by what happens when the other dog leaves. A dog who wanted to greet stays keen and bouncy. A dog who wanted distance shakes off, or goes quiet, or stares back down the street.
Find the distance your dog can think at
There is a distance at which your dog notices the other dog and can still take food from your hand. That distance is the whole method. Inside it, nothing is being learned. Outside it, everything is.
Stand somewhere dogs pass at a predictable distance, like the edge of a park or a quiet junction. Bring soft food your dog rarely gets.
When a dog appears, offer a piece of food. If your dog takes it, you are far enough away. If your dog cannot, move back 15 feet and offer again.
Note the distance that worked. For most adolescent dogs it starts somewhere between 30 and 60 feet, which is further than owners expect.
The 3 seconds that do the work
The exercise is small. Your dog sees the other dog, you feed, the other dog goes away. Repeated at a workable distance, seeing a dog starts to predict food and a check-in rather than a lunge.
The moment your dog spots the other dog, before the leash tightens, say their name once and feed at your knee.
Feed for as long as the other dog is in view, one piece at a time. Stop the moment the other dog is gone.
Do this for 4 or 5 passing dogs, then go home. That is a full session, and it takes under 10 minutes.
Do not wait for a sit. You are not asking for anything yet. You are paying your dog for noticing a dog and staying able to eat.
What to do when one appears with no warning
Turn and walk the other way before the leash tightens, feeding as you go. A retreat you choose is not a failure, it is you keeping the distance you need.
If you cannot retreat, step behind a parked car, a bin or a hedge. Two feet of visual block is worth twenty feet of distance.
If your dog is already lunging, stop asking for anything. Get past, get calm, and count it as a rehearsal you would rather not have had.
The part most owners skip
Stop letting your dog drag you into every greeting. If reaching the other dog is what pulling has always produced, the pulling is being paid every walk. Greet on a loose leash or not at all, and greet perhaps one dog in five.
This is not unkind. Adolescent on-leash greetings are tense and brief for most dogs, and skipping them costs your dog very little.
Safety note
Get a veterinary examination if the lunging arrived suddenly, or comes with growling, snapping or freezing. Sudden behaviour change warrants a veterinary check, and pain often shows up as a change in behaviour rather than as a limp.
Why not a corrective collar for this one
A tightening or shock collar delivers something unpleasant at the moment your dog sees another dog. A review of aversive methods found them associated with worse welfare outcomes and no training advantage. Reward-based methods are what the veterinary behaviour guidance recommends.
Today's version, in one line: find the distance where your dog can still eat, then pay them for every dog they see from there.