Even if you have a large, fenced in, private property, all dogs need to learn to walk on a leash. This is not about training your puppy to “heel” or not to pull, or to walk at your side and sit when you stop walking. Yes, all of that is what I teach as a professional trainer for dogs, but right now, I only want to talk about introducing your puppy to a collar/harness and leash and helping him to learn to accept it and be comfortable with it, and eventually relate it to doing something he likes.
So, where do we begin? I always recommend starting in the house. Simply put the collar or harness of your choice, on your puppy, and let me wear it in the house under “eyes on” supervision, while you’re playing with him. Distraction is always thought of as a “nuisance” and disruptive when trying to train your pup. But trainer or pet parent introduced positive distractions can be most helpful in some situation. Playing with your puppy, is an extremely helpful distraction when trying to teach him to wear a collar. Squeaky toys, balls and fetch are my favorites.
Once your puppy has adjusted well to wearing the collar or harness, maybe a day or two, attach a 6 foot, thin, lightweight, narrow leash that has a small clip; small being the operative word. If you use a heavy, thick, twisted, rope type leash, it will have a heavier clip, and a heavier clip will pull on the puppy’s neck or make a harness more uncomfortable. 
Now let the puppy drag the leash around while playing fetch or other distracting activity. Periodically, hold the leash in one hand and the toy in the other hand and entice your puppy to follow the toy. (Squeaky toys work great for this.)
Try this too. If the puppy is confined or if another family member can help, put the puppy’s leash on and walk him to his food bowl at mealtime. You might be wondering why I don’t mention offering treats to make your puppy walk on a leash. Anyone who knows me, knows that I do not use or recommend or condone the constant use of treats to bribe a dog to respond correctly. As a trainer, I’m OK with giving a dog a treat occasionally for good work. However, there are many other healthier, effective and rewarding ways to train, but that’s something I will talk about at another time. If you prefer to give your puppy a treat to encourage walking on leash, I yield to your decision. It’s just not something I prefer to do. What I do prefer to do is use a happy, encouraging tone of voice, call the puppy to come with me and stop a pet him and give him belly rubs and offer him his toy; thereby letting him know he’s doing a good job.
If the puppy is old enough to go outdoors, meaning your veterinarian has advised that it’s OK to take him for walks outside, you might find that the puppy will not walk very far from the front of your house. This is not unusual. In fact, I see this happen quite often. So, try this. Carry your puppy away from your home; let’s say half a block. Put the puppy down and chances are, he will walk home. Take the squeaky toy outside with you and use it to encourage the puppy to walk forward.
If your puppy walks a short distance and then plops himself down on the sidewalk, don’t stand there trying to convince him it’s not a good idea or just laughing. Both enable him to do this even more. I have seen this in action and trust me it doesn’t work. If you can’t use distraction to get him up and walking, bending down on one knee, at leash length, is the friendliest body language you can use when training your puppy. It’s the best way to get a puppy to come to you, or in this case, up and walking to you. Praise him and immediately continue your walk. If all else fails, physically but gently stand him up and restart him.
After walking home is successful, keep walking down the block in the opposite direction and don’t stop at home. As with all training practice, do this for 10-15 minutes, 3 to 4 times a day.