This is a running joke in the service dog (and positive training) community. When your dog does anything wrong, you should roll up that paper you're about to hit him with and smack yourself instead. This means either you weren't paying attention to him and he chewed up your shoe or you rewarded him at the wrong time and now he thinks 'lie down' means 'chase the cat'. I had a minor newspaper moment during my last session. I totally forgot to bring treats on our outing. Now he didn't misbehave, but he might have been a little more focused if I was luring something under his nose.
My training philosophy is 100% positive reinforcement. This doesn't mean I let him get away with anything. If I want him to come and he doesn't when I rig my bell, no treat. there's no "you tried so here you go". When I ask for a behavior I expect for him to do it. If he doesn't we move on to something else or wait 5 seconds and try again. I think one of the most common misconceptions about positive reinforcement is that you let your dog do whatever he wants and reward him for it.
Positive reinforcement also builds a strong bond because you dog wants to please you. All dogs have some sense of wanting to please their owner so if you work from there you will have an even more devoted dog. This is especially important for service dogs. I can't physically dominate my dog (not that I want to) so my dog has to want to work for me- not be intimidated or threatened into working for me. I can't just jump out of my chair and alpha roll him (a horrible technique where you flip him on his back and yell him into submission).
Dominating techniques like the alpha roll, yelling, hitting, and forcing will ruin a service dog in training. This is because they will be afraid to trust you and you can't have a scared service dog. Scared dogs can pose a threat to the public because they may lash out and bite if they feel overly scared or threatened. So the quickest way to wash out your service dog is by using those techniques.
Tomorrow we are having our first restaurant experience. I'll be armed with a Nylabone to keep him busy.