Praising works well but if you dont' happen to catch the pup then you can always take the pad and dab a bit of the pee on it so it's scented..even though I think that most pads are supposed to be lightly scented to attract them. That is what I had to do with my Shih Tzu to teach him. After that and I told him potty here Hobbs he learned that is where I wanted him to go.
