Young puppies can’t hold their bowels & bladders for long. If you come home to find that they’ve had an accident in there it’s quite possible that they can’t hold it that long. Generally puppies can hold their bladder for about one hour per month of age. So your 3 month old pup can probably only hold their bladder for about 3 hours. If you’re going to be away at work for long periods of time see if you can get a neighbor, relative or dog sitter to come over to let your pup out during the day.
You can use potty training pads to give a puppy a place to go inside. They are usually scented in order attract dogs to urinate on them. This can be an aid in potty training and may seem necessary depending on your situation. But, it can also cause some problems that may prolong the training period and make it more difficult. Using pads can confuse a puppy into thinking that it is OK to go inside.
If you want to prevent accidents before they happen you’re going to need to watch your pup at all times, including every time they wander off. It only takes one accident to set your training back. Now I know that watching your puppy non-stop isn’t exactly fun & exciting, but being able to catch them before they have an accident is why this method works so well.
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.
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.