Using vocabulary that your puppy can understand

Your Japanese chin absolutely thrives on consistency. This applies from finding and sticking to the best food to deciding from the start what is and what isn't acceptable behavior. Consistency, proper and prompt discipline, and keeping yourself as the undisputed head of the house makes a much, much happier and manageable puppy. The bouncy, frequent change lifestyle a lot of people enjoy is fine for them, but not for dogs.
Maybe you need to have a family council every few months to figure out what behavior is and is not acceptable to various members of your family. You definitely need to get all the human members of the family on the same page when it comes to discipline. If one person gives in to, and thus encourages, begging and another punishes your puppy for it, he will be a confused mess. Once everyone agrees on what is acceptable and not, enforce your rules. Letting your puppy do it "just once" will put a wrecking ball in your training program and confuse him.
Your Japanese chin will arrive with almost no vocabulary or a very limited one. Decide on your words of command and have the whole family use only those words. If you wonder why your poor silly puppy doesn't get the message when you go chattering away in your own vocabulary, try having everybody use the same words and see if it makes a difference. If different members of your family are uncomfortable using a phrase, "go potty" for example, if they use another short, easy to understand term, consistently, then your puppy will easily understand both of you and do what you want her to.
Another good general purpose word that has been used over the years is GENTLE. Said calmly and drawn out, it sounds like the behavior we want. This is especially useful when the puppy is playing roughly, a calming hand accompanied with the "Gentle" command will quiet your puppy. The puppy doesn't need to stop what they're doing- they're just doing it too much or too vigorously. The curious puppy that is nosing a resident cat will be warned to be "gentle". The puppy and cat need to get along, this is not a time for NO.
A puppy who greets someone very energetically is toned down, with the "Gentle!" warning. The older dog obviously knows what they are doing wrong when they get the gentle command if they're to rowdy. Think of the "NO" command as the red light and "Gentle" as the yellow, or warning, light. A very useful command.