Pulling on the leash is a natural thing to a dog because they walk faster than us. They see things differently than us both in color and perception. (No they are not color blind as many believe. They see in shades of blues, grey, yellow, green. They see red as black)
The largest difference is the sense of smell. Dogs smell individual scents. You may smell the cheeseburger, but the dog smells the beef, cheese, ketchup, onions, pickles, all individually. If you think about it that has to be really weird to smell that way. That is why they are able to use their nose in so many situations that we really do not even truly understand.
Did you know that a dog can smell their owner from 4 miles away? So how the heck are we going to expect them to go out and learn how to walk on a leash in areas they have never been, and are bombarded with smells. Especially smells of other dogs!
We need to start slow, and in an environment we can control. Your yard is the best spot for this. So today we are combining how to play first to make yourself the one they want to be with, and then working on focus with the off leash obedience. If your puppy is not paying attention to you, then you have to make yourself more exciting. If they still are not, play a game of hide and seek with them. You hide where you can see them to make sure they are safe, but they can not see you. They will finally realize you are gone, once they do wait just about 30 seconds and come out from hiding and call them to you. Make sure they are coming to you, not you running to them. They will quickly realize they need to keep an eye on you, or you might just get away!