When training people for a commercial pilot certificate, take some time to teach your students how to treat passengers well.
Passenger pampering is a rarely taught but essential knowledge nugget. After all, at least some commercial activities involve (or will involve) paying passengers, and if they become praying passengers, they won't be happy. The commercial pilot who can make passengers comfortable has a wing up in the job market.
Teach your commercial students that in the case of unusual maneuvers, it's best to explain to the passengers what you're doing before doing it. If you're making a short-field takeoff, let passengers know what to expect when you lift off. If the flight will encounter bumpy weather, take a moment to explain how the airplane is more than capable of handling the bumps. Inviting questions is a great way to quell passenger anxiety and increase passenger loyalty; teach your students to do it.
They should be taught to consider the physical as well as the psychological. Rapid descents can present inner-ear problems. Does anyone on board have a cold or sinus problems? It's best to know beforehand. If headsets aren't provided, how about keeping a set of unused earplugs for the "decibel sensitive"? They'll appreciate the consideration.
Being a commercial pilot is more than just knowing how to do commercial maneuvers. It's also about having concern for your passenger's physical and psychological well-being. In fact, I don't recall ever having a passenger complain about the sloppy way a chandelle was performed. I do, however, recall passengers saying that a pilot scared the heck out of them and that they wouldn't be flying again any time soon.