Aside from the obvious answer – not before you are ready – the time to get a dog is when you have completed your doggy education. And when the pup is ready.
An important consideration is the age of the pup. Most puppies change homes at some time in their life, usually from the home where they were born to the homes of their new human companions. The optimal time for a puppy to change homes depends on many variables, including his emotional needs, his all-important socialization schedule, and the level of doggy expertise in each household.
Leaving home can be traumatic, and limiting the pup’s emotional trauma is a prime consideration. If the puppy leaves home too early, he will miss out on early pup-pup and pup-mother interactions. And since the first weeks in a new home are often spent in a doggy social vacuum, the developing puppy may grow up undersocialized toward his own kind. On the other hand, the longer the puppy stays in his original home the more attached he becomes to his doggy family and the harder the eventual transition. A delayed transition also postpones all-important socialization with the new family.
For many puppies, eight weeks is the right age.
Eight weeks of age has long been accepted as the optimal time to acquire a new pup. By eight weeks, sufficient dog-dog socialization has taken place with mother and litter mates to tide the puppy over until he is old enough to safely meet and play with other dogs in puppy class and dog parks. Yet the puppy is still young enough to form a strong bond with the members of his new family.
Excerpted from “Before You Get Your Puppy” by Ian Dunbar.
This is spot on. I see these puppy mills trying to sell their puppies as early as 4 weeks, and it breaks my heart.