Dogs bark for many reasons, including boredom, in play, aggression, fear and as a form of protection or warning. Expect your dog to bark in these situations. If the barking is excessive, your pet will benefit from basic obedience training that includes ways to reduce barking behaviors.
Preventing Barking Through Training
Making a loud noise when barking occurs or teaching a "no bark" command may be helpful as well. Dogs should be taught to lay or sit quietly on command with positive reinforcement methods. Contact a qualified obedience trainer for additional suggestions.
If Training Fails
You can also view Banfield's handout on excessive barking, which offers solutions for territorial or reactive barking.
Other Canine Behavior Tips:
Why do dogs bark?
Stop your puppy from biting
Separation Anxiety in Dogs