Puppies would much rather play with leaves and bugs than go potty, if you aren’t there to see that you won’t know your pup needs to go back into his crate and come out again 5-10 minutes later! He will learn to sneak away, and have accidents inside. If you leave him outside for an extended period of time, chances are when you bring him back in he will need to go outside again soon or have an accident.
If your dog isn’t giving you an obvious signal that they need to go out (like whining at the door) I suggest teaching them to ring a bell when they need to go outside. Some of the other signs dogs give that they need to go out such as pacing around or circling can be easy to miss if they’re in another room, which is why a noise based signal such as ringing a bell can make things easier.
Be persistent! Make sure the puppy doesn't get the opportunity to pee and poop by using a leash indoors or confining him to a crate when you're out. Depending on the puppies age, pop him outside every 20 - 30 minutes, so there's a greater chance of him toileting outside (by accident at first.) In addition, get rid of any scent markers he's left by peeing or pooping indoors, as these will draw him back to the same spot. This means cleaning the area daily, for 2- 3 weeks after he last pooped there to fully get rid of any lingering odor that the dog can detect.
Unfortunately, there is no magic length of time or milestone age when a puppy can be considered fully housetrained and there are many factors that go into how quickly a puppy can be potty trained. Your puppy’s age plays a major role during the initial phase of potty training, as a very young puppy won’t have the muscle control necessary to hold it for long periods of time.
^ Vranica, Suzanne (September 10, 2009). "'Dog Whisperer' Hopes to Lead Pack at Newsstand". The Wall Street Journal. Archived from the original on November 7, 2017. Almost half of USA's consumers already know who he is, and consumers' awareness of Mr. Millan has grown 12% since May 2008, according to Davie-Brown, an Omnicom Group company that tracks the appeal of celebrities.
Don’t punish your dog if they pee inside. Regardless of all those old training ideas punishment isn’t a good deterrent for house training. Yelling at your dog after the fact just confuses them and makes them nervous around you. If you catch your did in the act you can try to get their attention & move them outdoors. If you’re successful & they continue going once you get outside praise them like crazy.
Remember that training is an ongoing process. You will never be completely finished. It is important to keep working on obedience training throughout the life of your dog. People who learn a language at a young age but stop speaking that language may forget much of it as they grow older. The same goes for your dog: use it or lose it. Running through even the most basic tricks and commands will help them stay fresh in your dog's mind. Plus, it's a great way to spend time with your dog.