The most important thing is to understand the pitching motion from a biomechanical perspective. If you have a good understanding of that, there aren't many problems you won't be able to diagnose and correct. And Coach Pauly has it exactly right....the hardest part is finding the cue or phrase that makes it click in the student's brain. My mentor once told me you don't really teach anyone to do anything. You set the stage and phrase things in a way that they can figure it out for themselves.