We have had our puppy for about 6 weeks and have been unsuccessful at house-breaking him. We are at wit's end.
We have been doing strict crate-training for about 4 weeks now. It has worked to some degree - when he needs to go, he starts crying and whining in the crate, and he will immediately eliminate when taken outside. Even though he's young (16 weeks), he doesn't have accidents in the crate, and doesn't need to go out more than every 6 or 8 hours or so.
The problem is when we let him free in the house (which we only do after he pees and poos outside). After a variable amount of time (as little as 40 minutes) he eliminates in the house without giving any kind of warning. He seems to have reached the conclusion that going outside is mandatory, but going inside the house is optional and perfectly acceptable.
He is very smart, and we have trained him to do lots of other things -- play fetch, sit, stay, respond to his name, and to stop biting. It's just this house breaking thing that has been an issue.
UPDATE: It's been an additional 2-3 weeks since I posted the question. He finally seems to be learning that it is unacceptable to go in the house, although he's really bad at telling us that he needs to go outside (he just sort of starts glancing at the door). The bell hasn't worked for us since he considers it the world's greatest toy, and just wants to ring it constantly. But we will find another signal and finally get him house-trained. This was a long road.
A trainer told us that it takes as long for a dog to un-learn a bad behavior as he was allowed to exhibit it. So by her theory, since he was going in the house for about 3 weeks, the first 3 weeks of crate-training was just erasing, and getting us back to zero. That makes sense given how long we've had to spend doing the crate-training.