Go to the door. Ask "do you want to go outside?" or whatever you usually say. Then use his paw to ring the bell, give immediate treats and praise lots all while you take him outside. Do this until he catches on.
Some it may take a few times, others it may take weeks. The more you practice, the shorter the time, so I would do it even if he is not asking to go outside on his own.
__________________ Mario  was adopted May 2015. Now he is a service dog and brother to Bailey the Airdale mix  |