Puppies are educated by the mother in a way that they learn to accept discipline. If a puppy didn't learn to accept leadership in his interactions with other dogs of the litter, his training would be more difficult later. Puppies who are separated too early from the nest, will have a tendency to be more nervous, bark and bite more and also to be less receptive to discipline. Often, they are more aggressive with other dogs. In general a dog who is sold to a pet shop or introduced to a new home before the age of seven weeks won't achieve his full potential as a good dog and companion.
At seven weeks the puppy's brain has reached its full maturity. However, his capacity of concentration has not yet fully developed and his attention span is shorter. But, he can learn! Not only what is taught him but what he sees around him. At this age the training is easier. Everything he comes into contact with will make a permanent impression on him. Behavior taught at this age will be permanent. It is important to remember that your puppy will grow and anything that you will not tolerate later must not be accepted at this age. This is also the best age to start the training in a non-punitive way, taking into consideration his physical limits and his short capacity for concentration.
In general, avoid stressful situations and continue to socialize and to train your dog in a positive and non-traumatic way.
Serious training, if it hasn't already begun, must be started now. It will be easier for the dog to realize that you are the master. When you assume the responsibility to buy a dog, you also assume the responsibility to train him and to become his master. By training and some specific exercises, you will learn to become the chief of the band.
The above is generally the same for all dogs, without consideration for the breed or the size of the dog. The next critical stages will fluctuate depending on the size of the dog and at what age they will reach maturity. In general, small dogs experience these stages earlier than big dogs for which the development is slower.
This period generally persists for a couple of weeks to one month and depending on how you handle your dog, it will make the difference between a dog who comes or not when you call. During this period think about attracting him positively, rewarding him generates an even stronger interest than the one that draws him away. Too many people make the mistake of punishing them for escaping right after they come back, the only thing the dog will remember is: to come = punishment. This fact will cause you a lot of problems later.
However, until you are sure of your dog, keep him on a leash. Don't give him any chance to run away, if you don't do this, it will only encourage his bad habit.
To be able to better cross this period, be patient, be kind, don't force your dog to make something who fear him. Tempt again to demonstrate him patiently that is no reason to justify his fear, permit him to face them positively. Over all continue your trainning on the same way, to procure him a certain leadership on a reassuring and familiar manner.
If at maturity, your dog tries again to test you, handle him firmly and continue the training. Train him regularly during this period of testing, encouraging him if he answers correctly to your expectations.
Many dogs don't show a noticeable change during this period, but if it does happen, you will be prepared and will be able to understand what is going on. Don't be afraid, use the same training methods you used before with all the firmness you need. You and your dog will go through this period with no serious problems.