There are entire books on this subject, and as many methods as there are dog trainers. My method draws on Pat Miller's 'management' techniques - if you don't want your dog to do X, then don't let him.
Dusty is never being given the opportunity to go to the toilet in the house. This of course depends on my being able to watch her 24/7, to confine her when I can't give her 100% attention, to keep to firm feeding, sleeping and playing routines, and to be aware of her 'bio-rhythms'. I also think it is important to have a specific place in the garden as a toilet area. 'Outside' is a fairly nebulous concept, particularly with my slate tiled living area and brick tiled garden.
I have a square metre patch of mulch near the back door which is the designated area. Sometimes we walk down to the larger area near the compost bin that Thommo uses, and eventually I'll get rid of the other one. At 1:00am on a winter morning the back gate is too far away. I think it is important to go with her, to make sure she goes, and to reward her enthusiastically immediately she does. There is not much point in rewarding a dog for coming back indoors.
Duzz has been a little gem so far, even taking herself out to the mulch on occasion. It helps of course that Deb and Rosie had between them developed an understanding that the garden was the place where these things happen.