PART ONE OF TWO—–
First breeders will tell you the good things about their dogs and leave out or down play the bad. All breeders do not all do this intentionally but it is just like parents and their children. There is a term for breeders who only see good in their dogs. It is called “kennel blindness”.
Some of the things you want to look for in a good breeder are that they compete their dogs, preferably in a similar discipline to what you want to do with yours. If you want a hunting dog then Hunt Test or Field Trials is what you want your breeder doing; of course actual hunting with their dogs is better. In some breeds, like the Chesapeake, you can look at what others have down with their pups or what is further back in the pedigree. In labs and especially Golden Retrievers it is best to have the pedigree and competition of the breeder in your favor.
Do they invite you to meet their dogs, the parents as well as others they may have. Many times the sire (dad) will not be available due to someone else having ownership of him.
Do they only use studs that they own or co-own? Line breeding is fine but in my opinion you want to see out crossing about every 3-4 generations, to much line breeding is another sign of kennel blindness. Do they want to control your breeding rights. Co-Ownerships and limited registrations have their place, but is the breeder normally selling their pups in one or both of these ways? If so they may be telling you that they know they have big problems in their lines and want to control breeding or give themselves a scapegoat when something comes up.
Health clearances vary some between breeds. The best thing to do is if you have decided on a breed; Chesapeakes, Labradors, Goldens, Curlys and so on you should consult the National Breed Club on what clearances are recommended.