It's important with all dog training but especially with young puppies to use lots of encouragement, praise and rewards (positive reinforcement) in your training. Start your puppy training sessions as soon as your little puppy arrives at your home - it's never too early. Set your puppy up to succeed, concentrate on developing desirable habits in your puppy and preventing undesirable behavior. It's much a better alternative to put your puppy on the right path from the start, rather than trying to correct established problem behaviors later on.
Imagine your puppy running out the front door. You call him, waving a treat. But he'd rather chase a squirrel into the road than come back to munch on a treat. In addition to the obvious danger of Puppy getting hit by a car, he learns that he doesn't have to listen to you. He learns that he's in charge of what he decides to do and what he decides not to do.
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.
If your pup barks: Some dogs have the habit of barking at other dogs while on a walk. Oftentimes, this behavior comes as a result of lack of exercise. Make sure your dog gets the proper amount of mental and physical stimulation for his age and breed. If this is still a problem, use the same process as you would if your dog is lunging, as described above — create distance and offer treats before he starts to bark, so every time he sees a dog he gets used to turning his attention to you.
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.