Method #1: Give Fido time to figure it out
This method will definitely work well if you've already started umbilical cord housetraining. It's also the best method for dogs who aren't very excitable and owners who don't want to get Fido worked up and would rather take the patient approach.
If you've already started umbilical cord housetraining, your dog's probably partly trained, though you might not know it. Keep Fido on a leash at all times so that you'll notice when he's getting restless and might need to go potty. Up until this point, you've been taking Fido out as soon as you think he might need to go potty. You make this decision based on his behavior, which he may have already noticed - he paces or whines or looks at you, and you notice him and take him out. All we need to do now is increase the strength of the signals, focusing on the barking and whining so that the signal becomes impossible to miss.
Weeks 1-2: A Little Whining
The easiest time to train is first thing in the morning when you know Fido needs to go out. Park yourself in a chair, Fido tethered to you, your morning coffee in hand - and prepare to wait. If your dog acts restless, normally you would get up and take him out to prevent an accident. Don't. We're going to push your dog into a stronger indication, ideally a whine. It's possible he'll have an accident instead. If he does, correct him as previously outlined in the corrections article. If you have to correct him, take him outside immediately and end your morning's training, knowing that tomorrow he'll be less likely to have the accident.
Most dogs will not immediately have an accident; rather, they'll make some attempt to get your attention. If Fido makes the slightest whine, immediately give him your full attention, tell him "Let's go outside" in an excited tone and hurry him out for a potty. This shows your dog that his voice has power. In the beginning, you want to notice and reward every single whine with a potty break. After a week or two of this, your dog should be whining pretty quickly first thing each morning to let you know you should take him out. He may even start whining throughout the day to get out.
Weeks 3-8: Crank Up the Volume
Once you're sure your dog understands the whining, occasionally ignore that first whine like you didn't hear it at all. Your dog should then whine a second time, often louder than the first. Immediately respond to this second whine, showing him that his persistence pays off. The next few times he whines, respond immediately so that the training doesn't discourage Fido. Ideally, Fido won't know if he has to whine once or six times once the training is complete. This will make him confident on those occasions when you truly don't hear him and he has to make more noise to get your attention.
Over the next month, gradually increase the amount of noise you expect from Fido, moving from two whines up to four or five some of the time. Still, mix it up enough that you sometimes respond to the first whine. During this month, you'll probably find that your dog sometimes barks, rather than just whining. Great! Always reward the barking so your dog sees that barking is a very powerful attention-getter. Also, now that your dog is doing so well with the training, don't let him out to potty unless he tells you he needs to go. (Of course, you can make an exception if you're leaving the house and need to let him out so he can go before you're gone for hours.)
Next, begin practicing without holding the leash. Starting first thing in the morning again, lock Fido in a room with you so that he can't wander too far. Keep your eyes on him (in case he tries to make a mistake) and wait for the indication that he needs to go out. Ideally, he should come to you and whine, not go to the door. If he whines at the door, try to wait until he is near you again and whining before you reward him. If you start rewarding him for whining at the door, you'll lose some of the benefits of the training. If he keeps whining at the door, go back to tethering him to you a while longer and concentrate on rewarding Fido only when he is whining and looking at you.
Weeks 8-12: Moving It Around
Part of the reason you've been working so hard to teach your dog barking is so Fido has a way to tell you when he needs to go out. He's getting close to being finished now, but what happens if you shut him into a different room in the house? Will he know how to bark there, too? Or at your friends' house? Before this training is complete, we need to present Fido with a series of challenges to make sure that he not only barks at the door when you're standing there, but also when you're gone or when he's locked into other rooms or in other houses.
Begin challenging Fido by shutting him into a new room with you first thing in the morning and sitting down and ignoring him. He may begin barking immediately, recognizing the setup. He may be unsure and decide to wait it out. If he decides to wait it out, you'll need to, too, so make sure you start this on a day when you have lots of time to wait. Keep your eyes on him in case he decides your forgetfulness gives him license to potty in this new room. At some point he'll remember his earlier training and whine or bark. When he does, leap up, praise him and take him out. Let him do his thing and praise him. Practice this challenging step every morning for a couple of weeks. When he gets good in one area, let him have a few great days and then move on to another room.
After a month or so of training loose in a single room, Fido should be very confident about telling you when he needs to go out. As long as he hasn't has any accidents for the last month, it's time to start giving him more freedom. Fido should alert you if he needs to go out. If he makes any mistakes (or has a history of sneaking off to make mistakes), you'll need to incorporate a spying program to catch him so he knows this isn't an option. Most likely, he won't make mistakes, because he now knows how to get outside when he needs to. Do make sure that you're careful in new houses or parts of your house where Fido hasn't been allowed before. Many dogs think they only need to keep their own areas clean, so keep your eyes on him anytime he is in a new place.
The final test is a different house. When Fido is perfect at home - in all the rooms, all the time - plan a sleepover at a friend's house. Keep your eyes on Fido the entire time he's in the new house, as many dogs don't think they need to keep any house clean other than their own. Be ready to catch any mistakes so Fido learns you disapprove of all pottying indoors, not just in your house! In the morning, get up and station yourself close to the door that leads outside, waiting for Fido's bark before you take him out. If Fido passes this test with flying colors, pat yourself on the back. Your training is complete. If not, try to practice in some new houses whenever you have the opportunity until this part of the training is clear.
Weeks 13-1,300: Maintaining the Training
Once Fido is reliably barking to tell you he needs to go out and is consistent about doing it all over the house, you should need to practice very little to maintain his training. You can go back to a more normal schedule of taking Fido out several times a day, which may mean that he doesn't bother to bark to go out, knowing that you will be taking him out at particular times. But be aware that he does need to be ignored occassionally to make sure he'll alert you if he has to. If you go too long without him barking, it's possible he'll forget his training - or get lazy and have accidents again. Make sure you occasionally "forget" to take him out and let him practice his barking so it remains a skill he uses on a regular basis.
Also make sure you think about Fido's housetraining anytime you visit a new friend's house, go on vacation or move to a new house. Changes in routine often prompt housetraining setbacks, so don't get caught sleeping: Practice your housetraining when Fido has changes of routine and ensure an accident-free lifestyle.