Internet websites like:
are low cost or free to people selling dogs. There is no policing of breeders on these sites.
Negative reviews can be removed by the seller (breeder) on these sites so you are not likely to get valid information about the seller.
AKC has a list of breeders that go through some vetting although not enough in my opinion.
If you use any of these sites to find a puppy you must do your research before purchasing. Never, never purchase sight unseen.
Contact the breeder using the method that they have provided.
If it is email be sure to ask for a phone number so you can speak to the breeder. When you speak to them politely get the following information:
Google the address and check out the street level map.
Always visit the breeder's facility. Never ship a puppy from a breeder that you have not fully checked out.
Remember, even if you get references from a breeder chances are that person didn't actually visit the facility.
Tell the breeder you want to visit and schedule a day/time that is convenient for both of you. Show up early. If possible the day before your scheduled visit.
Ask to see where the dogs sleep, eat, and play. If you see another building ask what is inside. Be firm but polite.
Google the animal control organization for the breeder's county.
Visit the website and call them. Tell them you are interested in purchasing a puppy from the breeder and ask them if there have been any reports logged for the address you were given.
Ask for a copy of the reports (this is public information)
Infodog.com has a database that is regularly updated of dog shows and participants.
You can look up any dog that was shown by their kennel name or their AKC Registration number.
This feature is not free however it is a small price to pay to validate what a breeder is telling you. (Deluxe membership is about $8 a month and you can cancel anytime)
The AKC does not police breeders. It is a database for dog registration. The only thing they check is whether the dog being registered has AKC registered parents. They don't check for inbreeding or health testing. The database is maintained by each breeder. A breeder can enter anything they want with little chance of the information being validated by AKC.
Don't rely on the AKC to make sure your breeder is legitimate.
If the breeder has had any problems in the past chances are someone has posted a negative review somewhere on the internet.
Google is going to be your best friend.