Study film, but also read. There are many excellent books on film theory and film-making. These are some of the quintessential reads:
And anything on Sidney Lumet, Walter Murch, Billy Wilder, Orson Welles, Hitchcock and Kurosawa. Watch and study their films. On Film-making: An Introduction to the Craft of the Director, Alexander Mackendrick. Into the Woods, John Yorke. Screenwriting 101, Film Crit Hulk! On Directing Film, David Mamet.