As I discuss at length in The Problem, too many hitters' swings have been, and continue to be, ruined because too few people are asking what I think is The Question.
What do the best hitters in the world do?
However, given the state of the game, I'd add a qualifier to The Question.
What do the best hitters in the world (actually) do?
Despite the rapid proliferation of high-quality video, an amazing number of people, especially at the highest levels of the game of baseball, have little to no idea how the best hitters actually move. Part of the problem is too many coaches are still using their eyes, and the human eye simply isn't up to the task.