Here are 2 articles that explain and define puppy mill operations
http://dogs.about.com/cs/generalcare/a/puppy_mills_are.htm
http://www.almosthomerescue.org/puppymill/puppymill.htm
A reputable breeder ...
2. Does not breed multiple breeds. They breed because they are passionate about their chosen breed and want to improve it by breeding healthy puppies.
3. Will give the intended puppy buyers a full review of the breed, including drawbacks of the perspective breed first, such as potential health problems and exercise requirements.
4. Will have bred the litter and have at least one of the parents for you to look at. Good breeders allow new puppy owners into their home (where all the animals should live) to view living conditions of all their dogs, be leery of anyone wanting to meet you some where other than their home to hand over the pup. Also be cautious of breeders that have a "show room" set up where the puppies and the litter's parent(s) are viewed yet they have other buildings on the property you are not invited to view.
5. Do not ship brachicephalic (flat faced) puppies under 12 weeks old during hot months of the year. Green MT. Bulldogs does not ship.
6. Never sells animals to a pet store. Breeders caring nothing about the health or temperament of an animal often breed pet store livestock. Their only goal is to make a profit. These animals and their parents often live in substandard conditions outdoors with little or no human contact until the animals are shipped to pet shops. Puppy mill "breeding stock" is not the best quality and often has congenital health issues that are passed on to many of their off spring. This is the reason reputable retailers like PetSmart and Petco do not sell puppies.
7. Does not advertise puppies on a website where puppies are mass marketed with other breeds and breeders on one giant web sight like puppyfind.com, puppy4you etc. Also as reputable breeder does NOT breed multiple breeds.
A reputable breeder ...
8. Breeds for sound temperament and health. Testing may be done on patellas, palate exam, heart exam, hearing, thyroid and more. A "Health Certificate" from a veterinarian is only a piece of paper the vet signs after taking your pup's temperature and looking for obvious signs of disease stating he examined the dog and it appears to be free of disease at the time of examination. These health certificates are required by air lines before they will allow your pet on the plane, but some breeders try and represent this paper as proof your dog was health tested by a veterinarian. This certificate has nothing to do with health testing to find a congenital condition that may show up months after you have your pet.
9. Screens the homes their puppies will go to live. Puts the puppy's well being as the number one goal.
10. Will have a sales contract and written health guarantee between the buyer of the puppy and the breeder of at least one year. This document will outline exactly what is expected of you as purchaser of the dog and what you can expect of the breeder as seller of the dog. This contract should protect you and the breeder of any hidden agendas.
11. Will explain average yearly cost of care for that particular breed. Proper amount of exercise, reasonable confinement, amount of food to feed, etc. ... before you purchase the dog.
12. Always be willing to answer questions long after you have paid for the dog and have taken it home. They should welcome and expect updates on the progress of the puppy's life.
13. Will be your best Veterinarian. The breeder should be well read in medical problems of the breed they are selling/placing. Should see more of your particular breed than your veterinarian. The breeder shares experiences with other breeders that are tried and true for their breed. Veterinarians have a general knowledge of most pets, however, a breeder specializes in his/her own breed. The breeder has extensive knowledge of health issues of their chosen breed, and may be able to guide you in areas where your veterinarian cannot. Breeder should be able to recommend a veterinarian in your area that is familiar with the breed you are getting from them.
14. Will have AKC litter registered pups and not FCI or APRI that can be converted to AKC. Papers come with the puppy and not after they ship you the puppy.
15. Will provide at least a 3 generation pedigree to all puppy seekers before they purchase the puppy. Will have on the average at least one champion in EACH generation.
16. Is well respected by other breeders in their breed and belongs to breed specific organizations that educate and protect the breed.