Use a crate:   It is one of the best investments you can make!  Crates are not cruel;  dogs are den animals and instinctively will choose to sleep in an enclosed, safe area.  The crate is their "bedroom".  You can put a blanket and toys in with them.  Often, once the dog is used to the crate, he will choose to sleep there.  When you are not able to be watching the dog, when you are at work, when you are sleeping, or just out of the house, put the dog in his crate.  By using the crate, you are reinforcing the dog's natural instinct of not eliminating where he sleeps.  It is important, therefore to use the right size crate.  If you have a massive crate and a tiny dog, he can just go to the opposite corner to eliminate!  As soon as you remove the dog from the crate, take him immediately outside.  Chances are, the dog was sleeping and will now have to eliminate.  The added benefit of the crate is it will also protect him from all the trouble he could be getting into in the house!  When the dog is beyond the chewing and housebreaking stage, you can start to wean him out of the crate if you choose.  Some people use the crate for a few months and then put it away for good.  Others keep it as the dog's "room" forever.

Do not paper train:  By paper training you are giving the dog mixed signals.   It cannot be OK to go indoors sometimes and not others!  Also, paper training is just one more thing that you have to teach--skip it!  Take the dog outside.

Use the same spot each time:  At least during the housebreaking phase, take the dog to the same spot each time and use the same word for elimination (mine is "piddle"!).  The dog will associate the smell and the word and realize what he is there for.  Do not walk or play until the "work" is done!

Go outside frequently:  As soon as the dog wakes up, as soon as he leaves his crate, first thing in the morning, last thing at night, after meals, if he is sniffing, even if you think that he looks like he might be thinking about it--GET HIM OUTSIDE!   The idea is to get him doing it right all the time--you are not giving him a chance to make a mistake!  Yes, this is a pain, but your perseverance will pay off!

Praise, Praise, Praise:  Just as you would for any other behavior, be generous with the praise when your dog is doing well!

Correct the dog properly:  Do not rub your dogs nose in a mistake!!  It will confuse the dog and it is downright nasty!  You can only correct the dog if you actually catch him in the act.  Then grab him by the scruff of the neck, give a gentle shake and say "NO" firmly.  Then immediately take the dog outside to his "spot".  Never correct the dog if you do not catch him in the act!!   The dog has forgotten about his mistake.  He just knows that you walked in a room and then scolded him.  He will be confused and begin to act "guilty" whenever you arrive home.  Many people condition their dogs to have the "guilty" response! 

Clean mistakes thoroughly:  Dogs have highly developed senses of smell.  You may no longer be able to smell the mistake, but he can and will return to the scene of the "crime".  Clean thoroughly with non-ammonia products...there are many on the market developed to eliminate pet odors.