Let me throw in a biggie: HOW something is communicated to a pupil is ENORMOUSLY important, making "changes" either impossible, unrealistic, or at the other end of the continuum, immediate.
A real teaching situation will make my point: I witnessed the head pro at one of my courses giving a lesson. He correctly told the pupil that he needed a bigger turn, and that he needed to get the club "up here further." But his inability to do it at the lesson, where he was told to "go home and work on those changes" was absolutely impossible for him. NOT because he was incapable of making the changes, but because the ROOT CAUSES OF WHY HE DID NOT DO THOSE THINGS were left in place (probably from mandates of former instruction or beliefs because of the generality of instruction that fails to allow the golfer to question the "fundamentals")--so "trying" will not only be fruitless at home as it was at the lesson, HE WILL BE DESTROYED BY THINKING HE CAN'T DO IT.
The solution, then, required addressing three elements: "with your feet closer together, you can make that turn, see?" (wherein the pupil clearly could immediately have made the move asked of him), "With your hands like this instead of THIS, you can put the club HERE." (where with that slight adjustment the wristfold would have been installed immediately) and 3) THE SPECIFICITY OF EXACTLY WHERE TO PUT HIS HANDS AND CLUB which would so change the "try to do..." indefinite, unspecific, unidentified exact thing which can be made so clear, was left out.
TRYING is useless: having SPECIFICs is didactically the only way to help someone; and if you do not uncover the mandates that prevent a motion (wherein the golfer is still following advice deeply embedded and unquestioned) the old will interfere with the new and over-ride its installation.
It does no good to try when the intention of the golfer is trying something different. And "try" is evidence that how to perform the correct motion is not understood BY THE TEACHER.