Anyone who flies with me regularly learns the basics - thats all there is to it.
passenger briefings should always include seatbelt use and door opening and closing procedures this is obvious to us... but how many pilots brief passengers on symptoms of hypoxia if it is to be a flight at higher altitude? how many brief them on the symptoms of carbon monoxide poisoning? that they should alert you to how they are feeling? and how to disengage the heater when its a cold day and the heater will be used?
As pilots with a regular passenger who flies with us very frequently it is a great idea to get them comfortable with how to switch the transponder code, how to set a frequency into the radio and how to set up the GPS to go directly to an airport, these should pretty much be the first lessons a regular passenger learns. they are simple steps that most would find as easy as using a smart phone, but to a lay person it can feel like a big deal to learn how to properly do these things not only is it a great confidence builder to move into "hold the yoke for a moment" - but they are potentially important life saving skills in an emergency that sees you incapacitated.
"hold the yoke for a moment"... that has often times ultimately provided the regular passenger with the knowledge of how to hold altitude, climb, turn, descend and control speed with pitch and power changes.
they dont have to be an ace of the base, but arming them with this minimum knowledge you accomplish two things.
1. you now have a hell of a co-pilot that you can enjoy flying with on a different level
2. you give them a fighting chance should anything happen to you the pilot as more than an unseen illness can incapacitate you.
when i was instructing regularly back in the day, i used to offer a course to spouses, it was about 10 hours of flight time and concentrated mostly on aspects related to Climb, descent, turns, landing and GPS navigation if applicable. The passing criteria was basically that us, and the airplane had to survive the landing.
i only had a hand full of takers over the years, but any pilots here on the boards might consider asking a CFI if he or she offers something similar. a story like this drives it home.
best to have it and not need it, than to need it and not have it.