First step is to have puppy walk beside you without a leash. Bring a treat and puppy will happily trot along in hopes to get the treat. Next do the same thing only attach puppy with a leash. Sometimes a harness is a good way to go if puppy pulls at the leash and pretends to be a bucking bronco.
When puppy pulls stop the fun. Stand still and have him sit nicely. When he looks at you to ask 'what happened? ' begin again and when he pulls stop and have him sit again.
With young puppies they will quickly learn this is dumb and begin to look up and pay attention to you so that together you can explore the world.
Older puppies are often not so motivated. Our puppy Lexi sits and pulls, sits and pulls. My mum put a halti on her, it is called 'gentle leader'. Some people think it's really really mean but the little cloth halter around her muzzle just makes it not fun to pull. In five minutes she was walking like a dream instead of pulling mum down in the snow....so nobody got hurt.
Hopefully she will soon learn the habit of walking nicely and the halti will go back in the closet.
I enjoy walks still although being pregnant I don't want to walk so far.