There are some helpful hints that can be given for problem barking.
1. Try to NEVER reward barking. If the dog barks in the yard, wait until a brief moment of silence before opening the door and calling the dog in. Remember that negative attention is better than no attention at all; if you open the door to yell at the dog for barking, the dog may prefer the scolding to sitting in the yard alone and bored.
2. Avoid the things that cause barking. If the dog barks at dogs or people on the street, make an effort to block the dog's view of the street. Many dogs that are problem barkers in the yard would be happier in the house, and this is a lifestyle choice that should be considered. Dogs are a highly social animal, and being isolated away from the other pack members (the human family) can be highly stressful to the dog.
3. Do not use an anti-barking shock collar. These increase the dog's anxiety level, and they don't work very well (nor do other punishments help).
4. The most effective method for controlling barking is to INTERRUPT the barking and then replace it with a different behavior. Bark collars that release a citrus-scented spray when the dog barks are a form of this method. It helps if the interruption is not perceived as coming directly from the owner (which may be a response that encourages barking). A quick, light spraying with a garden hose or a quick blast of an air horn can be used to interrupt the barking, then call the dog to you and give a series of obedience commands for which the dog earns a reward.
5. Obedience commands (sit, down, roll over, etc ) are very helpful and should be used frequently during the day, even when the dog is not barking. The first reason for this is that it helps establish the person's dominance over the dog; if the dog feels that his social position in the pack is lower, he will feel that he has less "right" to bark. Giving these commands also changes the dog's focus from what HE wants to listen for what YOU want. And it is fun to perform commands, particularly when appropriate rewards are given frequently.
6. Some dogs bark excessively because of "separation anxiety", a panic attack disorder that sometimes takes the form of EXTREMELY persistent barking when left alone. These dogs will sometimes bark for 8 hours straight, causing severe physical and emotional stress. Separation anxiety requires a completely different approach and should be treated with your veterinarian's help.