When you are doing dog training simple commands are the best kinds to use. They are easier for puppies and dogs to understand. This concept is generally taught in an obedience training class, but it can take some time to get the hang of doing this. As an example, imagine you are in a training class where the sit is being taught. All over the room, you may hear people saying the word repeatedly, so if the puppy or dog isn't completely confused, he may come to the conclusion that he isn't supposed to sit until he hears the word three times!
The purpose in sticking to simple, short words for commands is to help the pet develop a habit of recognizing and responding. Canine behavior has a lot of habitual aspects to it -- as does human behavior, come to think of it! When your dog training is based on using simple words that you repeat once per request, this is easier for the animal than if it has to guess at your meaning as you chatter away.
Of course, dogs can pick out words that way if they want to, as anyone knows who has had a conversation with another human is which they said something like, "Shall we take Buddy to the park?" Buddy may easily pick out his name and perhaps the word "park." The domestic dog has had a lot of practice in listening to human speech!
So use one-word, easily pronounced commands -- which, by the way, are also sometimes called cue words. That expression gets away from the idea that you have to be the boss and the dog has to obey! While there are certainly times that do call for obedience, such as when you need the dog to come rather than go into the street, by and large the best dog training evokes willing compliance from the dog.
With a new puppy, training goes best with simple words. Sit, stay, come, down... use these classic training commands and you are off to a great start.
By the way, since "down" means something like "Get onto the floor," what do you say when your dog is jumping up on people and you want him to stop? A good word is "off."