A dog is said to have learned a command (word, sound, cue) once he has associated it with and performs a specific action. The simplest way to teach a word, for example, is to say it while he is executing the desired behavior. If you say it clearly (Once, so it fills the air and you know he has heard it distinctly), the dog will naturally bind the cue to the movement, so when he hears it the next time, he will do it.
Whenever we come home, I will find Cooper sitting at attention, waiting for my command, as I slide back the door of my van. Back in the day, I’d release him with a “That’ll do” and he would leap from the car, make a mad dash across my lawn, leap over a bed or two of flowers, grab the sidewalk, then disappear around the side of the house, his tail waving like a flag behind him. Being the human that I am, it would take me a bit to catch up with him, but there he’d be, waiting for me to go in to the house, through the kitchen door.
Since his response was entirely predictable, I knew if I substituted the word “Back” for the release phrase “That’ll do.” he would learn the new sound. With a gust of breath my pursed lips separated, and out came the clearest “Back” ever spoken by man and off he ran. His response was perfect. In a short time he successfully associated the sound with the act. Now, I can say "Back" anywhere within view of the house and around back he goes.
I since taught him the word “Front” by standing at the front door, calling him to me, and saying “Front” to him as he drew near. Now I can count on Cooper heading to the front or back door, from the car, upon request.
Although simple, this is not easy for everyone to understand at first. The trick is, the behavior has to be in place before the cue can be associated with it and the cue must be delivered unambiguously.