Having a dog constantly bark is very annoying for your neighbors, and stressful for you.  But how do you get them to stop? 

A lot of dogs don't realize that continuous barking is unacceptable.  It is possible your dog is bored more than anything else.  Be sure to give your dog lots of walks so he can explore the sounds and smells of your neighborhood.  He needs plenty of exercise, a big place to run, lots of toys, and possibly a digging pit to call his own.  Bored and under-exercised dogs will bark to keep themselves occupied.  You might want to consider training as well.  This will exercise your dog's mind, keeping him out of trouble.

If your dog is alone during the day and barks while you are gone, purchase one or two toys that dispense food.  You place the food inside of it and as the dog chew on the toy, he is slowly rewarded with food.  This will keep your dog's mouth occupied with better things than barking.  If your dog is barking from the back yard and people walking by, cover the front fenced area with a fence the dog cannot see through - or place a tarp temporarily over the fence until the dog is trained.  If your dog barks from the window at people passing by, keep the window closed while you are not around.

Once a dog starts barking, it becomes a habit.  You need to teach your dog that non-stop barking is not allowed.  Have a pocket full of treats at hand, and begin the training.  As soon as your dog begins to bark, tell him NO BARK.  He will probably stop to look at you, which is when you immediately give him a treat.  Tell him GOOD BOY NO BARK! and give him lots of scritches.  When he barks again, say NO BARK.  The minute he stops barking, give him a treat and tell him GOOD BOY NO BARK!  Keep up the process, and make him wait longer periods of time between NO BARK and the treat.  These periods can be only a matter of seconds, but he will eventually get it.  Dogs minds are very simple.  He needs to associate NO BARK with love and a treat.

If you are not able to get your dog to initially stop barking for the first treat, try and get his attention.  You can raise your voice firmly, but never hit.  You can also spray a bit of water at his face... anything to get him to stop barking if only for a moment.  That is when you immediately give him the treat, the GOOD BOY NO BARK, and the praise.  It takes patience, but this process will work.  Never raise your voice during this training - always keep calm.

For bark control, ultrasonic bark control units are available for purchase.  Placed within 10 feet of where your dog barks the most, it emits an ultrasonic tone when it registers a dog barking.  This tone will startle your dog and cause it to stop barking.  You can also use this unit for training purposes to stop unwanted behavior.  It is helpful in keeping your dog out of the trash, off the couch or even from chasing kitty.  

You can also purchase a similar unit that attaches to the dog’s collar.  The collar emits a loud sound which will stop your dog in mid-bark, but will not harm him in any way.  This unit actually goes where your dog goes – an especially helpful tool when he is playing in the back yard.  Additionally, there are units which emit an herbal spray when a dog bark is sensed that attach to a collar.

There are shock collars available for "training purposes."  StrongPets.Com does not recommend them.