Watch for bait & switch scams, especially when someone is delivering a puppy to you.Make sure the puppy that is pictured is the one that you are getting
Health testing can be verified on OFA , all you need is the registered names of the parents.
Puppy mills advertise in the local papers using a local area code
A good breeder will offer Health Guarantees
A good breeder will insist on first right of refusal if you cannot keep your dog