Dogs for sale from a pet shop or breeder allow you to take your time and find
exactly the dog you are looking for. 
If you are particularly
interested in a specific breed, you will probably need to buy a dog rather than
finding one at a shelter.
Decide whether you want a puppy, which will need to be trained, or an adult dog. Consider things like typical breed temperament, shedding tendencies, and energy level before deciding which dog is right for you.
It is always best to bring a pet into a stable environment. Be sure you have the time to devote to a new dog. If you are planning a vacation, a move, or a new baby, wait until you are "settled" again before bringing home a dog.
The Internet is a great resource for locating dog breeders. Look for
breeders' own web pages, and bulletin board and listservs of dog groups that
give feedback about particular breeders. While you may be able to buy a dog
through the classifieds, this may not be the ideal forum. Some reputable
breeders advertise in the classifieds. Other sellers, though, may simply be
dissatisfied owners. Try to find out why the previous owners are selling the
dog. A dog show may be a good place to find dogs for sale. Try to visit the show
when the crowds are thinnest (weekdays, early in the morning may be a good
time), to allow you time to talk to breeders and check out the dogs in a less
stressful situation. 
Your local vet may also be able to recommend a
reputable
breeder or dealer.
Always make sure your breeder keeps sanitary and pleasant conditions. The dogs should appear well-cared for and well-fed, with ample free space to run and play, and clean cages. Look for an active, alert dog with clear eyes and nose. The fur should be clean and soft, with no bare patches or tangles. Only buy a dog from a breeder you feel you can trust. The breeder should be as interested in the dog's welfare as you are. A reputable breeder will provide you with a copy of any agreements in writing, along with a written guarantee regarding your animal and should clearly explain any return policies. If your breeder fails or refuses to do this, find another breeder.
Be sure the breed of dog you decide to buy matches your lifestyle and environment. Some dogs, especially long-haired breeds, require a good amount of grooming such as daily brushing. Others do not require as much, but all breeds of dogs will need love and attention.
