Consider checking with a breed rescue first. A simple Internet search will generally turn up the web page for the national rescue club for any popular breed. Just type in the name of the breed and the word "rescue."
To find a local breeder, contact your local kennel club, or check with the American Kennel Club. Your veterinarian or pet store may also be able to direct you to a breeder.
Be cautious of breeders who breed more than one breed. These breeders are often really puppy mills. Look for a breeder who earns titles for her dogs and does genetic testing of her breeding stock, such as OFA x-rays for hip dysplasia, CERF testing for eye problems, BAER testing for hearing problems, blood tests for thyroid function, or other conditions known to be common in a specific breed.