Help for a Barking Dog
This one can be a little tough. You can try to interrupt him with a clap or sound and then be sure to reward him for being quiet. If he's barking at you, just ignore him or walk away. If he's barking at other things you need to figure out why and help him. If he's scared, startled, or excited by it then additional socialization and training can help bring down his reactivity level. More exercise usually helps as well because he'll have less energy to be barking. The most important part is rewarding him for being quiet and trying not to yell at him when he's barking (if you're yelling, he'll see it as joining in and raising the excitement level). With patience and consistency you should see improvement.