Leaning for takeoff
I remember the same method. Full power, slowly lean for peak, and enrichen it enough to assure smooth operation.
Lean for taxi, too, to prevent plug fouling.
My instructor taught me that at shutdown you should bring the power up, I don't remember to which RPM, lean the mixture for a few moments, and then shut down the engine. This method supposedly burns the carbon off the plugs. I had other instructors and people tell me just to kill the engine with mixture and not worry about carbon.
In flight, lean to peak EGT if you have it and richen the engine enough to assure smooth operation. If you don't have an EGT, lean until just when the engine runs rough and richen for smooth operation. Of course, POH recommendations trump any of these suggestions or other old wives' tales you hear about leaning.