Once you've established an association for your dog (or other animal) between the sound of your chosen marker and some valued reward, you can begin to use the marker to identify and encourage any and all behavior you like. If you have a totally untrained young pup, you might mark and reward a moment's quiet in an outburst of barking, then the next moment, and the next, until you find that the moments accumulate into longer spells of sweet silence.* Moments of eye contact are another great place to start with puppies and many full-grown dogs: everything you do in training will be built on a foundation of focused attention, so make it as wide and deep as you can. Don't worry at first about attaching cues to these behaviors. Saying "quiet" before your dog has arrived at a solid physical understanding of what quiet is will only create needless frustration for you both. And saying "QUIET!" will probably convince him that whatever he's barking at is even more threatening or exciting than he thought, since you're suddenly barking too.
If your dog already performs one or more behaviors pretty reliably when you ask for them, you could begin simply by marking correct responses to your cue. What's correct? For now, whatever it has been in the past. If your dog habitually responds to "sit" by backing up a couple of steps and settling lazily onto one haunch while sticking his other back leg out to the side, you know that's his definition of the word. Yours might be different, but for the moment you can set aside the task of bringing the two definitions together. Mark and reward every sit that follows your "sit," no matter how slow, no matter how sloppy. (You may find the sits get quicker and straighter in spite of your absence of effort.)
A few things to remember:
- Give the cue only once. If your dog fails to respond, wait at least twenty seconds (and until you have his full attention) before giving it again, or "Sit. Sit. Sit!" may become your cue. Treat all words like empty vessels, and fill them deliberately with meaning.**
- The mark is always followed by a reward. You don't have to mark every repetition of the behavior (I'll talk later about effective "schedules" for marking), but when you do mark, you're making a promise on which you need to deliver.
- Work on one new behavior at a time. There's a significant exception to this rule that I'll talk about later, but this helps avoid confusion for the animal and accelerates learning.
- Work in short sessions. Very short! Ten to fifteen repetitions between breaks. At the first sign of fatigue or fading interest, stop.
- End on a high note. If possible, end with the new behavior you've been training, but if necessary end with a behavior the dog already knows well. Success breeds success.
*On the other hand, I do not recommend that you begin by marking and rewarding a bark, especially if you're using a more powerful marker like a clicker. One thing to keep in mind is that the first few behaviors you effectively marker train will become the animal's default behaviors in future training. Quietly attentive behaviors (like eye contact or sit) are your best choices at the start.
**The trick with words (and other cues and markers) as vessels of meaning is that they might already be topped up. Old meanings can be difficult to dislodge, especially if they're loaded with pain or fear. Thus it's a very good idea (though sometimes difficult in practice) to avoid saying your pet's name in anger. If you want a truly empty word, try something rare, silly, or foreign. I lived in Bologna more than twenty years ago, and pretty much the only time I get to knock the rust off my Italian these days is when I'm cueing Pazzo with "fusilli!" (left spin) or "bombolone!" (right spin).