Power Steering: Teaching Dogs Not to Pull On the Leash
While this video shows a new puppy learning that pressure on the leash is a cue to turn toward the handler, this same technique can be used with dogs that have a long history of dragging you down the street.
To be successful, take a break from walks (if possible) and replace that time with trainning, gradually building up to the sidewalk outside.
Teaching a behavior is not what creates well-behaved dogs. It's practicing that behavior in gradually more difficult situations, setting your dog up to be successful. The more they are reinforced for the behavior you want, the more their behavior will improve.
Tip: A great place to work on leash training outside is a big, empty parking lot. There are fewer smells and other distractions for your dog.