The process is the exactly same for older dogs as it is for puppies; prevent accidents from happening by using baby gates and a crate if possible, create a predictable schedule, learn to recognize your dog’s potty signals, accompany your dog outside and immediately reward for all outdoor elimination, properly clean any accidents and supervise your dog until you’re sure that he understands the rules.
Strictly following the model set out in the Koehler Method of Dog Training, some 50 years later, the Koehler method continues to be taught in both class and private training formats. The method is based in the philosophy that a dog acts on its right to choose its actions. Koehler explained that a dog's learned behavior is an act of choice based on its own learning experience. When those choices are influenced by the expectation of reward, the behavior will most likely be repeated, and when those choices are influenced by the anticipation of punishment, they will most likely cease. Once the dog has learned that its choices result in comfort or discomfort it can be taught to make the correct decisions. Action→Memory→Desire encapsulates the learning pattern used by the method; the dog acts, remembers the consequences, and forms the desire to repeat or avoid those consequences. Adherents believe that once the behavior has been correctly taught, it should be performed, thus making any correction, fair, reasonable, and expected. While the model has been used consistently since 1962, some of the punishment procedures described in the book are now not considered necessary, humane, or appropriate by many trainers.
The principle behind using a crate for housetraining is that dogs are very clean creatures and don’t like a urine-soaked rug in their living spaces any more than you do. It’s important that the crate is the right size—just large enough for the dog to lie down, stand up, and turn around. If it is too large, the dog will feel that it’s OK to use one corner for elimination and then happily settle down away from the mess. Many crates come with partitions so you can adjust the size as your puppy grows.