Once you've made the decision to get a dog, you need to decide whether a puppy or adult would be the best choice. Each has its own set of benefits and drawbacks.
Adult Dogs: With older adults, you need to obtain as much factual history on the animal as possible, to know what you're getting. Find out how many homes the dog has had, at what age it was first purchased, and why it was relocated each time. Learn about the dog's good points, bad points, and its medical history. Ask how the dog gets along with children, with other dogs, and so on.
Unfortunately, even if you ask all the right questions, you may not be told the truth, particularly if the current owner really wants to get rid of the dog. Beware of dogs that are "free to right home." Expect to pay something, to show you're serious about caring for the dog. Beware of dogs that have had multiple homes and owners that say only good things about the dog. (No dog is perfect!)
On the plus side, if you find a good, well-adjusted adjust you may not need to deal with house training, or the exuberance and demands of a puppy. Take your time and make multiple visits to the dog's home before purchasing him. Expect to be interviewed by the prospective owners (if they really care about him), with questions about your family, life-style, accommodations, fenced yard, etc.
Older Puppies (5-12 Months): The primary caution here is buying a "show quality" puppy from a breeder that "kept him around a few months to see how he would turn out." This is a common, accepted practice, particularly with breeds that require full dentition, or size restrictions. Beware of the puppy that has been kept in a kennel the entire time and not properly socialized, housebroken or obedience trained. Lack of proper socialization and training during this time may lead to severe behavior problems, particularly fearfulness. On the plus side, you have a good indication of the animal's size and conformation, as well as his adult temperament tendencies. The dog may already be housebroken and obedience trained.
Younger Puppies (7-16 Weeks): Most animal behaviorists and trainers agree that 8-10 weeks of age is the best time to bring a puppy home, because of its ability to learn, adapt to new situations and bond with its new family. As the puppy ages past 7 weeks, it needs ongoing human and canine socialization to develop properly. If the puppy spends 24 hours a day from 7-12 weeks of age in a kennel or pet shop window without proper contact, it may have problems. Puppies that are removed from their littermates before 7 weeks of age also show behavior problems. They tend to miss out on lessons in canine behavior while playing with littermates, and they don't receive canine discipline from their mother. Never obtain a puppy younger than 7 weeks of age as the possibility for behavior problems later in life is significantly higher.
CAUTION: Animal researchers have found that many puppies go through what is called a "fear imprint" period somewhere between 8 and 10 weeks of age. During this time, try to avoid exposing the puppy to negative, frightening situations, as research indicates they are more easily imprinted during this period.