It's inevitable when you have a puppy or incontinent dog--your carpet will get peed on. It's easy enough to clean up fresh urine when you catch Fluffy in the act, but dried urine stains are more difficult to remove from carpeting because they can soak into the padding and dry. It's a three-stage process. First, you have to find the urine stains. Then you need to extract the dried urine, and finally, use an odor neutralizer to eliminate the smell.
Find the urine stains using a black light. Available at most hardware and some pet stores, black lights let you find dried urine stains you probably didn't even know existed.
Soak the stains using either undiluted white vinegar or enzymatic cleaner, using enough to penetrate through to the pad. Let it dry naturally. The odor will dissipate as it dries. Two treatments, spaced 24 hours apart, may be the most effective.
Shake baking soda over the area, covering it completely.
Mix 1 cup of 3 percent hydrogen peroxide with 1 tsp. dish soap. Pour it over the stain, and rub it in with a clean rag. Allow it to dry for at least an hour.
Vacuum over the stain to pick up powdery residue.