Does the breeder have only 1 or at most 2 breeds of dogs and only 1 litter at a time?
If there are several breeds of dogs, chances are the breeder cannot devote the time it takes to become really knowledgeable about the breed. If there is more than one litter at a time, it is very difficult to give the puppies the attention they need and may indicate that the primary purpose for breeding is profit, rather than a sincere desire to sustain and improve the breed.