Help him relax when he comes home. When your puppy gets home, give him a warm hot water bottle and put a ticking clock near his sleeping area. This imitates the heat and heartbeat of his litter mates and will soothe him in his new environment. This may be even more important for a new dog from a busy, loud shelter who's had a rough time early on. Whatever you can do to help him get comfortable in his new home will be good for both of you.
Puppies are highly social animals and spend most of their waking hours interacting with either their mother or littermates. When puppies are socialized with humans, particularly between the ages of eight and twelve weeks, they develop social skills around people. Those that do not receive adequate socialization during this period may display fearful behavior around humans or other dogs as adults. The optimum period for socialisation is between eight and twelve weeks; professional animal trainers and the American Kennel Club advise puppies should be introduced to "100 People by 12 Weeks" and have encountered a wide and varied selection of people and environments.
Your young puppy is totally reliant and dependent on you to help him habituate and fit into our human, domesticated world. Your guidance and leadership will determine what path his life takes and what type of dog he will become. During puppyhood you play the lead role and are responsible for shaping the character, temperament and behavior habits that your dog will carry throughout his life. Your puppy's future is in your capable hands...
Once your dog can stay, you can gradually increase the distance. This is also true for the “sit.” The more solidly he learns it, the longer he can remain sitting. The key is to not expect too much, too soon. Training goals are achieved in increments, so you may need to slow down and focus on one thing at a time. To make sure the training “sticks,” sessions should be short and successful.
First, teach the release word. Choose which word you will use, such as “OK” or “free.” Stand with your puppy in a sit or a stand, toss a treat on the floor, and say your word as he steps forward to get the treat. Repeat this a couple of times until you can say the word first and then toss the treat AFTER he begins to move. This teaches the dog that the release cue means to move your feet.
Just as a child needs a caring parent; an athletic team needs a coach; your puppy needs a leader and a clear social hierarchy. If you do not take up the role of leader, your dog will; and you will end up with an unruly, disobedient dog. Many people try to win their new puppy's love by letting the puppy always have its way. Buckets of affection is a wonderful thing for most puppies, but it must be tempered with respect.