One more suggestion...if you have multiple doors that lead to the outside. Pick ONE to use...eventually he will associate that door with needing to potty...and that will be the door he goes to on his own. That is when you will know...he's getting it.
Another...if he takes a nap or goes to sleep...immediately when he wakes up...take him out.
I also used the phrase ...go potty and pretty much had a potty party when they went. My Reese will potty on command and still looks to me for praise while he's going.