Choose a puppy based on its breeder.

When selecting a puppy for a pet, choosing the breeder may be more important than choosing the breed, suggests Andrew Luescher, a veterinarian and head of the Purdue University Animal Behavior Clinic, West Lafayette, Ind. "Not all breeds of dogs may be suited to you or your family's lifestyle, but for certain you want an animal that comes from a good breeder."

He recommends getting information on a number of breeds of dogs and narrowing your choice to a few possibilities. Then visit breeders, selecting one you trust and can go back to for help if difficulties occur. "Take a look at both parent animals and ask the breeder if they have been tested for problems that may be common to that breed. A good breeder will also give you references to others who have purchased puppies with a similar genetic background."

Some behaviorists have proposed procedures to test puppies for dominance, because a dominant animal may become more aggressive toward its master. However, studies show that dominance can't be detected in animals that young. "I suggest people choose a puppy that is friendly, one that doesn't show fear, and one that's outgoing and interested in you," Luescher says. One of the best ways for owners to avoid behavior problems is by enrolling their pets in puppy classes as early as possible. "Puppy classes teach animals how to interact with humans and other dogs. They also teach obedience."

The window of opportunity for animals to learn to socialize with humans is up to about 12 weeks of age. Puppies should be handled a lot while they are young, but should not be sold before they are seven to eight weeks old. He advises owners to be aware of another important stage in a dog's development. "Between eight and 10 weeks, puppies go through a fear period. If something significantly scares them during this time, they may be ruined for life."

Luescher estimates that between 40 and 50% of pets have some form of a behavioral problem, which accounts for a significant number of the animals surrendered to humane shelters each year. Among the most common are aggression toward the owner or strangers, separation anxiety, fear, and house soiling. All can be treated with behavioral modification techniques such as desensitization and counter-conditioning.