Effective methods to stop a dog from barking

1. Praise over punishment
© Pleple2000, Creative Commons Maltese going for a walk
© Pleple2000, Creative Commons

Need for attention
Dogs are much like children and they prefer any attention, even negative attention, over no attention at all. The most effective way to train a dog is with positive reinforcement.

Praises
For a barking dog, set up a few situations in which you know the dog will bark. You could have someone come to your door, or walk by you on the sidewalk when going for a walk.

If your dog begins to bark, give a command of "stop," or "enough." When you have your dog‘s attention and it stops barking heavily, praise him or give him its favourite treat or toy.

Keep practicing this daily until you see your dog learns to follow your commands.

Hint: Dogs have a better response to two-syllable words such as "enough."
2. Use a squirtbottle
© Courtesy of Linsenhejhej, Creative Commons dog playing with stick
© Courtesy of Linsenhejhej, Creative Commons

A squirt of water will take the attention off of the cause of the barking long enough to get your dog‘s attention.

Once the dog stops barking, make sure to reward it with a toy or treat.

Use only water in a squirt bottle.
3. The dog is left alone
© Photo courtesy of Ginny, Creative Commons Dog with toy to help with barking problem
© Photo courtesy of Ginny, Creative Commons

Toys
A dog barking because it is left alone all day, is usually due to boredom. Leave out extra toys when you leave.

This type of nuisance barking can be eliminated by providing something for the dog to focus its attention on. Special toys are made that you can fill with treats, but the dog has to work to get the treat by rolling it around into the right position.

Good-bye
Do not say "good-bye". Just leave. A dog will pick up on the word "good-bye" as a sign you are leaving and anxiety might set in which will cause barking.
4. Citronella collars
© Photo courtesy of Elf, Creative Commons Dog collars that help train dogs to stop barking
© Photo courtesy of Elf, Creative Commons

Citronella is a natural fragrance that is used in repelling mosquitoes. It also has a very unappealing smell to dogs. Citronella collars will sense the vibrations in a dog‘s throat when it barks and will emit a quick spray of the ingredient. This will interrupt the dog‘s barking. This is considered negative reinforcement and should only be used as a last resort.
5. Start early training your dog
© Photo courtesy of Almcwilliams, Creative Commons Boxer puppy train not to bark
© Photo courtesy of Almcwilliams, Creative Commons

Many times the cute behaviour of a puppy will evolve into annoying habits in the adult dog. The best time to take care of a problem like excessive puppy barking is when they are puppies. Make sure you give your puppy lots of attention and exercise, and carry that behaviour into adulthood. The best behaved dogs are secure and well-cared for.