I agree... break it down simple on what a clutch does. I taught like a dozen people how to drive stick in my car when I was in college.
Main reason, no one knows how to drive stick anymore. 2 of the people were to get "alone, make the girl nervous, then at ease time on a back road"
The rest were friends/roomates that I hung out with that didn't know how to drive stick, didn't have a car, and used to go to parties with me. I wanted more then one DD.
Just tell them the engine/transmission are connected. When you push the clutch in, it disengages the engine from the tranny. If you go to slow in to high a gear, or stop in first, the car transmission will drag the engine to to low of rpms and stall.
Tell them if they ever have any problem, or feel like they are losing control, stab the clutch in. Don't just pull your feet off the pedals. The clutch disengages everything.
At first, teach them to rev high like 3500 rpms, and slowly slide the clutch out and give less gas, feathering it, so they can "feel " it engage. Then shift at each gears. For slowing down,don't show down shifts yet, just pushing the clutch and stopping with brakes. Then move to downshifts for going around corners. Have them rev less high each time as they get a "feel" for it. Riding the clutch and some slight clutch burn smell isn't as bad as "popping" it.
If you have something with a v8, you may not have to rev to 3500 rpms, you can probaly do alot less, as it will take more to bog the engine.
In my old 5.0 mustang, I was showing my wife since she never drove it, and you could literally let the clutch out pretty quickly and the engine had enough torque to move the car and not stall. LOL
What kind of car is it. If its a Corvette, might be a little interesting to learn on that. Most everything else should be ok.