I'm Old, so;
1. My father taught me in the mid 50's with my first car, a 49 Chevy, in February. (This is why I don't have problems driving in the snow and ice ).
2. When I teach someone how to drive a manual, I first explain to them that I car is like two different things. First you have the engine and second you have everything else from the transmission back to the bumper. Then I explain that a clutch is nothing but a device that sits between the engine and the transmission, to connect the engine to the rest of the car. The left peddle on the floor is nothing other than the thing that operates the clutch. Once that is understood, then I show them that if an engine is running, and the car is at a standstill, you have to engage that clutch slowly, otherwise the engine will stop. I get them to practice stops and starts. Once they can do that, I then explain to them that once the car is moving, you have to shift to the next higher gear, so the car will go faster while the engine is going slower. First, disconnect the clutch, shift the the next higher gear, then reconnect the clutch. With practice, they get to do the shifting smoother. My wife always had trouble knowing which gear to be in when going around a corner. I told her that there is not one exact gear to be in, because it depends on your speed, and how sharp the corner is, and if she feels the engine is going too slow, to shift into the next lower gear. In time, a "light bulb" will go off in a new manual transmission drivers head, and they will understand how it all works.
The most important thing is that the Clutch connects the engine to the rest of the car.
Although this has nothing to do with all the above, the last two Renault Laguna's I leased on my last two trips to France, had the very best manual transmissions I've ever driven. They were like shifting through butter, unlike the last Manual I owned, a Honda Accord, which would grind when shifting into 2nd, 3rd, or when downshifting into 1st.