Understand your puppy's particular breed behavior and needs. Research your dogs breed traits and special needs or any behavior that you should be aware of and look out for. For example, If your puppy is a tiny little chihuahua, their bladder will be very small and they will need to urinate more frequently; accidents will happen even if they are well trained.
Many owners appear disappointed that their young puppy will not toilet when out on a walk, yet relieves itself the second it gets back home. This is because the puppy has been taught to toilet only at home (hopefully in its garden), and being creatures of habit, they often wait until they have returned home before evacuating their bladder and/ or bowels.