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.
Positive reinforcement is the key to success. A common mistake is to punish your dog during training or become angry. This will only cause confusion. You can try to hold your dog's attention with treats and enthusiasm, but know that it is time to end a session when your dog becomes bored or tired. Try to end sessions on a positive note. Eventually, successful training will be achieved with patience and consistency.
It also helps to teach your puppy a “potty phrase” when you take him outside for a bathroom break. A potty phrase is a way to gently remind your puppy what he needs to do when he’s outside. It’s a big help during the potty training phase of puppyhood and you can continue to use for the rest of his life. Pick a phrase like “hurry up” or “go ahead” and say it softly right as your puppy eliminates. In time your dog will associate the phrase with the act of elimination, so you can say it when your puppy gets distracted and forgets what he needs to do outside.
You should always accompany your puppy outside for potty breaks. You’re there not only to ensure that he actually goes, you’re also there to reward your puppy with a treat for going in the proper spot. Wait until your puppy finishes eliminating and immediately give him a tasty reward for a job well done. If you wait until you get back in the house, your puppy won’t make the connection between his elimination and the reward.
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.