Before you can even attempt to stop your dog from barking at everything that moves, you need to understand a few simple but important facts.

Once you understand these, getting them to stop is easy.

First, you cannot expect your dog to stop barking altogether. What you can  do is teach you dog when it is OK to bark and when it is not. You may even want to create a trigger word where the dog can bark on command. If you use a word which will trigger your dog to bark on command, you will greatly reduce the urge he or she feels to randomly bark without giving that command. For instance, train your dog to bark when you tell them "Rover, speak!"

Next, you want to move on to actually stopping your dog from barking when they are not supposed to.

Usually the dog is barking for a reason, even if it isn't blatantly apparent to you at first.

Sometimes they are trying to alert you of danger or trying to get your attention to something. The key here is to think about what it may be that is causing your dog to bark and acknowledge it (and remove it if necessary). Then acknowledge your dog by saying something like, "Thank you, Rover. I see the squirrel (as you point to it). Now that's enough barking." Use a firm, but very calming and polite tone. The dog should pick up on your acknowledgment and stop.

This method should get you started in the right direction to a well behaved and quieter dog.