Dog training  

Well, I'm not a dog trainer but here's my thoughts......

Commands for dogs and puppies are better if they are one specific word. And you should say their name before the command. So if you want him to stop barking, instead of saying "stop barking" you should say "Toby...quiet". Instead of "get off the couch" you say "Toby....down" Always put a pause between their name and the command. You say their name to get their attention then follow up with the command. And you have to be consitent. You can't say quiet one minute and hush another.

Work on one command at a time and praise them for all the good things they do too.

You could probably get one of those no bark collars, but you might want to ask yourself if this is something you really want to do because if you were having an intruder come in yourself you might want your dog to bark. It might not be good if the dog were not barking. I would think about what you really want to do.

Puppies are naturally naughty..
This might be 1 of the reasons of them barking.However some of the dogs are naturally playful and they may have this felling towards the strangers.Most of the breeds however are not used to strangers and they feel naturally protective towards their owners.Although they may be small in size however they do hav the pride to defend their owners.This factor has to be taken into account and you should try training the dog before they become too protective of your family and may later lead to problems as they may bark at strangers and scare them away. :D
Hope my note helps you in some way!!!

There are some really good books on this subject ucl. Try this sight. http://all-about-my-pets.com. Good luck :)

I usually use one word commands so that it's not something complicated that the dog is looking at you like huh. When my dog frost is barking I tell him enough .. If that doesn't work I go to where he is and then say enough looking directly at him and having a very stern tone in my voice once he is done I tell hit to sit in japanese and then tell him to lay down. That way I have him were he has calmed down ...

It depends on what type of dogs you have.I have a beagle and he is around with people since he was a puppy. And let me tell you this dog is so people friendly that if a thief come into my house he would follow the thief and wag his tail. i don't know if that you what you want. on a second though it may be good to consult a dog trainer