Be sure to go with him and watch him and calmly praise him when he goes. Don’t go crazy praising him, or he is liable to stop, just calmly let him know that he is good! It doesn’t matter if it is 100 degrees or 10 below zero; raining or snowing, if you don’t go outside and monitor your puppy, you will not know if or when he is going potty outside which means he is likely to come back inside and go potty.
A Hungarian dog training group called Népszigeti Kutyaiskola use a variation of model-rival training which they describe as the Mirror Method. The mirror method philosophy is that dogs instinctively learn by following the example of others in their social sphere. Core to the program is including the dog in all aspects of the owner's life and positive reinforcement of copying behaviors. Mirror method dog training relies on using a dog's natural instincts and inclinations rather than working against them.
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.
Every dog needs to learn to walk on a leash. Besides the fact that most areas have leash laws, there will be times when keeping your dog on a leash is for his own safety. Learn how to introduce your dog or puppy to the leash, then teach him how to walk properly on the leash, even beside you on a bike. A loose leash walk teaches your dog not to pull or lunge when on the leash, making the experience more enjoyable for both you and your dog.