There are many reasons why you need to train this behavior, but the biggest reason is that you need to have control in knowing your dog will always come to you when you call him. A great example is if your front door is opened and the dog was to run out, it is essential that you know that your dog would come back if you were to call him.
One of the greatest parts about training this behavior is knowing in the back of your mind that you have spent the time to develop a relationship with your dog. Because of this, your dog most likely wants to be with you, so training your dog to COME should be a fairly easy behavior.
But there are times when this behavior is a little more difficult to train. An example might be when you are teaching a dog that you adopted that might have had a bad history of training. Another example might come from a trainer just rusheda dog into training before a relationship was established. Once this happens, both training and the dog wanting to be with the trainer or owner can end up being a negative thing.
Either way your dog is going to need guidance. In teaching this behavior many people think that it is the fact that the dog knows that he is off the leash. They believe that the dog thinks that he does not have to COME because he knows there is nothing the owner or trainer can do.
They are somewhat right. More importantly, the dog needs to understand that it makes no difference how far away he is, he must COME when called. This is why I highly recommend using a long line. This gives you the control, and lets the dog know that it does not matter if he is 4 feet away or 14 feet away. He must COME when called. This is done with the long line, which is sold right here on this website.
As you train your dog put the long line on and let it drag. Say the dog's name, and follow it with "COME". If he does not come give a quick tug on the line. It does not have to be hard at all.
After a few sessions, your dog should start coming when called when the line is on, without you pulling on the line. Once this happens you can start to use a leash dragging intead of a line.
Once your dog understands you can then remove the leash. This can take a few days to a week.
MORE BASIC BEHAVIORS:
SIT - Using Gentle Manipulation
SIT - Using treats