Buddy is an inside dog (he is allowed on the couch) and toilet training was something we were a bit worried about. It was a lot easier that we thought! Dogs pretty much toilet train themselves because they have a natural instinct to want to keep their den clean. This means that they actually prefer to go outside to the toilet.
At this age (3 months in this photo) Buddy mainly had accidents when no one was home to let him out. Or sometimes when he was heading for the door but didn't quite get there on time.
PS at 4 months he was almost totally reliable with going outside. Now (at 6 months) he knocks at the door to be let out when he needs to go to the toilet. (smart dog!)