The process of training a dog is not really that hard at all. It is a disciplined work of training the owner. Many pet owners think of their pooch as another person but this couldn't be farther from reality. A dog is deeply ingrained with the instinct to be a dog. They don't try to fit into our culture or lifestyles, but they will automatically accept us into theirs whether we want to be accepted or not. Naturally, dogs have a hierarchy and if the owner isn't the leader of the pack then the dog will constantly act out and be very hard to train.
Being the pack leader to your dog(s) is a never-ending residual dominance that can be achieved in a few simple ways. Presence is everything with a dog. Wolves in the wild don't talk to each other like we do, but they still communicate through body language, scent, and presence. Since the owner likely lacks the ability to convert emotion into scents that are recognizable by their dog(s), they should stick with body language and presence which kind of fall hand in hand.
One simple way to find out who is the alpha in the owner's home is to see who consistently goes out the door first. Now once in a while a submissive dog will go through the door first because of minor discrepancies on the owner's part that may go unnoticed to the human eye. Generally, however, this will explain a lot. If the owner's pet does this they will want to make sure to exit before their dog in a dignified and mature way. They shouldn't be fighting with the dog to be the first out the door or this will make it a game to the animal and will make them not only dominant to their owner but also aggressively competitive.
Another thing that must be taught to ensure easier training is food dominance. If one's dog understands that their owner is giving them food as opposed to serving them training time could be cut in half. The way to do this is to make the dog sit and stay before they are to be fed. This will show the owner as the pack leader. The owner should make the dog sit if the don't do it on command and tell them to stay. If they don't, then they won't get food until they sit and stay which is easily taught through consistency and time. Eventually, the pooch will sit and stay automatically and any future training will come far more easily and the pet and the owner will have a more mutual respect.