While many dogs bought from newspaper ads and yard signs are healthy and happy, far too many are ill, poorly socialized, genetically flawed dog-catastrophes waiting to happen. When you are trying to screen prospective breeders, here are some questions that might be useful.
How long have you been in the breed? What others have you bred?
You probably want to avoid anyone who has "switched" breeds every couple of years, from popular breed to popular breed. Otherwise, look for someone with some experience with the breed you are interested in. If they are new to your breed, do they have experience with a similar breed?
Also, be very wary of people who have multiple dog breeds. It is not uncommon to find people breeding more than one kind of dog (for example, quite a few Akita breeders are also interested in Shibas), but a breeder producing litters of many different breeds of dog is not going to be your best source, and probably should be suspected as a puppy-mill or disreputable breeder.
What kind of congenital defects are present in this breed?
What steps are you taking to decrease these defects?
Avoid anyone who says "none", or "not in my dogs!". There are genetic problems that are present in almost every breed. Do some research here, and make sure you know what kind of answer you should be getting from the breeder.
A reputable breeder should be able to tell you what kinds of problems might be present in the particular breed (for example, hip dysplasia, entropian, thyroid problems, etc) and what kind of testing is available to find it. It goes without saying that the breeder should be doing those tests on all their breeding stock. Any dogs that are showing signs of any of these problems should not be bred -- avoid anyone who is breeding dogs with genetic problems, or who is not testing their dogs and bitches.
I can't stress enough that you need to have a good idea of what the correct answers are here. Get any good dog book, call the breed club, find out what to expect before you fall in love with that cute puppy face! A breeder that can't tell you what kinds of things affect their dogs isn't going to be breeding to avoid them.
Do you have the parents on site? Can I see them?
This is kind of a trick question - most breeders will not own both dogs. They will own the mother (and you should be able to see her), but the best match for that bitch probably belongs to someone else. So, if you can see both parents on site, you should be a little suspicious. It may mean that the breeder has a large pool of dogs and is carefully matching them - or it can mean that they had two attractive dogs in their backyard and had either a planned or unplanned breeding just because they had a male and female at the same time.
You should be able to see the mother and any other dogs on site when you visit. If the breeder hesitates, you should wonder why - are the dogs kept in clean, healthy conditions? are they too aggressive to let loose? You should be very comfortable with any reason not to see the dogs.
However, remember that you should not be interacting with very young puppies, and might be prevented from seeing puppies that are less than 4 weeks old. This is ok, and is simply the breeder trying to eliminate any chance of illness in the puppies - they don't know what kind of dog diseases you may be carrying, and don't want the litter to get sick.
What are the good and bad points of the parents? What titles to they have?
Usually, breeders will start to gush at this point and enumerate all the wonderful qualities of their dogs - and the best I've talked to also will point out their flaws. What you're looking for here is temperament, possible aggression, how they deal with people, how they're not "perfect".
As for titles, reputable breeders show their dogs, and they should be carrying points towards a championship, if not champions already. This is important - while there are many wonderful dogs out there that haven't seen the inside of a show ring, if the breeder is truly trying to improve the breed, they will be comparing their dogs to other breeders and trying to breed dogs that match the standard. The only way to do that is to show their dogs.
Many breeders compete in obedience as well, and will have Companion Dog (CD) or other obedience titles for the parents. Often, this is a good benchmark for temperament and behavior.
Can you explain the puppy's pedigree?
A good breeder should be able to tell you something about dogs on your puppy's pedigree. Have them explain the often cryptic letters and titles awarded, and get a good feel that they know the lines they are breeding from. At the very least, they should be able to provide you with a 4 generation pedigree and be able to tell you about the dogs.
You might see the same dogs listed a few times on the pedigree - the breeder should be able to point out any linebreeding and inbreeding and explain the benefits and dangers of both.
Where were the puppies raised? How have you socialized them?
What you're looking for here is an indication of what kind of socialization the puppies have had. Ideally, you want the breeder to have raised the puppies in the house, around the normal daily activities of a household so they are used to the noises and activity of humans.
Someone who says "in the garage" or "in the kennels" can also have well socialized puppies, but you need to be more careful. Have they spent enough time with the puppies?
Socialization is so important to getting a well-adjusted, well-mannered dog. Puppies should have been exposed to people, other dogs, new situations, normal household sounds and activities in order to learn. A puppy raised without this important social interaction can be shy, fearful, aggressive, or have other problems as they get older. Dogs need to know how to play, how to handle new situations, how to relate to people.
How many litters do you have a year?
Breeders producing more than 1 or 2 litters a year are probably not paying enough attention to the genetics and health of the puppies. If it is a small breeder, even two a year may be too much to be able to make sure that the breeding is going to be successful and produce healthy puppies.
Definitely avoid anyone who "always has puppies", or who is breeding their bitch every year. I have talked to several people with more than one litter at a time - I avoid them as well. If someone has three litters (especially if they note that it was "unexpected") on the ground at the same time, they are certainly not planning these puppies! All puppies should be "expected" and well planned. If they're not, it's a crap shoot as to whether you're going to get a good puppy or a nightmare.
What guarantees do you have for this puppy?
At the very least, the breeder should guarantee the puppy against any debilitating genetic problems, and insure that the puppy is in good health.
A breeder should be prepared to take any dog back for any reason - part of being an ethical breeder is making sure that the puppies have a good home and that it stays that way.
When can I take the puppy home?
Puppies usually go home between 8 and 12 weeks. Avoid anyone sending tiny puppies home. Puppies sent home too early don't have the chance to develop healthy interactions with other dogs, and can be sickly or hav problems eating. I often see people with puppies that are five or six weeks old -- these tiny babies are too young to be separated from their mother.