I'm not sure i want everyone else to teach like I do!
FWIW, I teach the 1/4 back turn for safety reasons. Off and on feel the same when you lock them. 1/4 off feels differently than those two and I like that. What I don't like is a DM turning my air off as he's checking it. That's happened three times now and I have learned to get to the back of the boat while keeping the DM in front of me and away from my tank. Three breaths and I fall back into the water frustrating their attempts to assassinate me.
I had that in Thailand. Had my back to the DM after I completed my buddy check. There was a delay whilst we moved dive sites, in the in-between the DM turned my valve off.
Its the first time anyone ever touched my kit, its generally not an acceptable practice. Especially cylinders, regulators and valves.