Editor's note: Victoria Stilwell hosts "It's Me or the Dog" on Animal Planet and is the founder of Victoria Stilwell Positively Dog Training, both of which advocate positive reinforcement during training.

(CNN) -- The shelter dog is often perceived as unpredictable and inferior to one that is bought from a pricey breeder or a pet store. The thought of giving a home to a dog with an unknown history also puts many people off. But while some dogs are relinquished to shelters because of problem behaviour, most are surrendered because of a change in the family situation.

Shelters can be overwhelming places to visit, so give yourself time when going through the adoption process and make decisions with your head as well as your heart.

Because stress levels can be high in such an environment, dogs tend to exhibit behaviour that does not reflect their true personality. Don't be put off by a dog that stays at the back of the kennel too tired or nervous to greet you, or by the dog that leaps at the kennel door like a lunatic as you walk past. Remember these dogs may behave very differently once out of confinement.

Look for a dog that recovers well when taken outside the kennel. One that runs and is excited to interact with you, your family and other people. If you already own a dog, bring it along and allow the two dogs to greet in an outdoor neutral area to see if they will be compatible. Look for soft, wiggly body language, warm eyes and a desire to play.

If the shelter dog that you like seems removed and not interested in interacting with you, retreats or stiffens if you try to touch him, looks at you with hard eyes or is tense around your existing dog -- do not adopt that dog.

Dogs that are relinquished to shelters because of behaviour problems can be difficult to re-home. Don't be afraid to ask the shelter staff about the dog's medical and behavioural history before it came to the shelter -- if known -- and behaviour while it has been in their care. Try to get more than one person's opinion about the dog.

Adopters can easily be swayed by a well-meaning employee or volunteer who is desperate to find their favourite dog a new home -- even if the match is not a good one. If the dog you like has known behaviour difficulties, ask the staff if they have been working with the dog on that issue and how the dog has responded so far.

Even if there are no obvious behaviour problems, here are some other important questions to ask: