Begin as soon as the puppy arrives in your home. Young puppies should be taken out immediately upon waking and just before retiring, as well as multiple times during the day. Most puppies cannot "hold it" for long periods so it will be necessary to take the puppy out almost every hour at first (especially after periods of play, naps, and mealtimes), and then gradually increase the amount of time between visits to the "bathroom".
Take the puppy to the same area each time and praise it immediately and enthusiastically when it eliminates. Do not play with, or talk to, the puppy until after it has eliminated. Remember, if the puppy doesn't eliminate outside, its urine and feces are being saved for deposit inside your house!