STEP ONE: ESTABLISH COMMUNICATION
Talk to your dog. Do you know how much he/she understands? When your dog first comes home with you it is as if he/she has been sent to a foreign country. Dogs know no English, French, Spanish, etc. They must be shown what each word/phrase means - EVEN THEIR OWN NAME! Dogs DO understand "dogspeak" - the tones and body language of canines. The easiest way to get a concept across to anyone (including a dog) is to speak to them in their own language. Since we are unable to bark, etc., the best we can do is use our tone of voice to communicate our desires to our dogs early in our new relationship. With proper training techniques, dogs CAN and DO learn not only English, but whatever languages their owners use.
Start with your tone of voice. Women have the easiest time with what I call the "Good Dog" tone of voice - the one that is most often high pitched, soft, sweet, and generally in a falsetto. Men have the easiest time with the "Bad Dog" tone - the one that is deep (but doesn't have to be!), stern, and sometimes gravelly. Men also have the easiest time with the "Command" tone - the one that is neither good nor bad, but has a firm (usually lower) tone. Try telling your dog that he/she is bad using the "Good Dog" tone; then try praising your dog using the "Bad Dog" tone. Watch your dog's reaction to each. Even if they understand some of the words, they generally react to the tone first.
Many people have a difficult time getting their dogs to obey their "Command" tone of voice. Often it is because they "tell" their dogs in the form of a question: "staaaaaayyyyy?" - with a voice raising at the end of the command. Remember, commands must be firm, short, and to the point, with the tone going down at the end, never letting the word drag on.
STEP TWO: BASIC TRAINING
To start to teach your dog your language, you need to combine the words with an action that shows the dog what you want, and some reinforcement - either positive or negative. Say your dog's name. Does the dog respond (look at you, wag his tail, move toward you)? Your dog should ALWAYS have a pleasant experience when s/he hears his name - NEVER unpleasant. Some people create a new "Bad Dog" name to use for those bad dog times. To teach the dog his name, position your dog close enough to touch, preferably on a leash so s/he doesn't move away. Say the name cheerfully and give his ear a tug, or his leash a tug toward you, or move his muzzle in your direction. When the dog looks in your direction, immediately use your "Good Dog" voice and praise and stroke your dog on the head or chest. Practice this until looking at you happens without the tug and continue to practice for the dog's entire life! It reinforces the communication link between the owner and dog.
Teach other words the same way. Simple one word commands work best. Say the dog's name (to get his attention - remember that communication link!), follow with a command, and then SHOW him what you want. PRAISE IMMEDIATELY when the action is completed - even if you MADE him do it! Eventually you dog will learn to respond to the command without needing to be shown - but you should never forget to praise!
STEP THREE: GETTING YOUR POINT ACROSS
Sometimes words are not enough when communicating with a dog. Since dogs must learn what each word means, all the other "extra" words are just a bunch of "Blah, Blah" to them! Consider the Gary Larson cartoon that shows an owner scolding his dog, Ginger, then shows what the dog hears "Ginger, blah, blah, blah, Ginger, blah...".
I have learned that a sort of modified canine language can get a dog's attention faster than human words. Those of you who have been dog owners probably have already learned just how insignificant the word "NO" is to a puppy. This is especially true if it is said frequently (kinda like kids, in that respect...). the word "no" to a dog is a nice soft word, with no sharp sound to it. Therefore there is nothing in the word to catch a dog's attention, or to stop them from continuing the action you wish to halt. I find a gravelly, growly "EGH!" (hard to spell a sound but it's like you are vocalizing while pushing air out of your lungs) can be used to halt activity. Or try "Angh, Angh!" - our sound for no, without saying the word - only say it with a growl, and sharply. That is also a good sound to use! If you are having problems with your dog mouthing you, try a very shrill and loud "OW!!", which ususally stops them in mid-chew! Their littermates and other dogs use sounds like that to set limits on mouthing behavior.
"Praise Sounds" are harder to create. My dog knows she has done really well when I say one of several words I reserve ONLY for really good work: EXCELLENT! or ALRIGHT!, or PERFECT! I say them very cheerfully, but not with the falsetto "Good Dog" voice. I will often follow any of these words with a beloved scratch on the chest, or an extra-special tidbit (small and chewy, not crunchy) that I use only for extra-special rewards.