There are many sources of information available that can help you find a reputable breeder. Here are a few:

1. Contact the American Kennel Club for breeder names. There is a breeder list available on the AKC website, under the specific breed you are looking for.
2. Contact your local breed club for a list of breeders that you can contact. Many of these can be found under the City Guides section.
3. Attend a dog show and ask a breeder. You can usually find high quality dog breeders at dog shows and after a showing, they are generally more than willing to talk to you about puppies. In fact, you may also be able to see sires or dams of upcoming litters at the show. Dog shows are also freqently attended by local breed clubs and rescue organizations, so you may also be able to find more information through these booths.
4. Ask your vet for breeder recommendations.
5. Ask friends who own dogs of your intended breed if they have any breeders to recommend.
6. Visit local shelters - county, city, ASPCA, and Humane Societies.
7. Check Petfinder.com: Adopt a pet and help an animal shelter rescue.
   Petfinder is an on-line, searchable database of animals that need homes. It is also a directory of over 2000 animal shelters and adoption organizations. It is possible to find a purebred dog as well as mixed dogs vs. buying from a breeder.

After you locate at least a couple of breeders, you will need to interview and visit each breeder to narrow down your selection.

A note of caution before purchasing any dog make sure you visit this site -- Beware of Puppymills.