Walking is a critical part of any dog's life, but it can also be a huge nuisance if your pup doesn't understand who's the boss.
To emphasize this, it's necessary to start as early in your dog's life as possible. This way, no matter the potential size of your dog, they are conditioned to not resist, or in some cases to not resist as much.
The methods to this range from fairly simple to extremely complicated, and everyone has their own way.
We have tried multiple training methods to get Marou to behave on a leash, though most have had little effect other than making him mad or irritating him.
First, we tried to stand still until he quit pulling on the leash, but all that did was frustrate him and tire us out. He also got choked a lot by his harness from all of the pulling and jumping to get away. This startled everyone around us and worried us because we didn't want him to hurt himself.
Next, we tried using slight leash tugs, and that had some significant results. This didn't give us any results at first, but as he has matured he has responded better to it. It's very important not to tug or jerk too hard on the leash, as doing so may choke your dog or even cause serious irreversible damage depending on the harness or collar used.
We've also tried simply picking Marou up and bringing him back inside when he doesn't behave, but we had little result with this, as he just got mad and got into trouble and destroyed some of our things.
There are many more methods than what I've posted here, and there are new methods created all the time, so everyone will have their own opinion.