Ball over brim of cap you must "open the gate" that means if it is to your left your left foot should drop taking your left shoulder away from home plate. Same move on balls hit to your right except it is right foot dropping.
If ball is below brim of cap hold your ground or step forward toward ball.
Know your field.... for Corner outfielders the ball will bend toward the line. Center fielders have to play slice and hook. Left hand hitter to left field gap will slice to LF line. In Right Center it will hook to RF line. Vice versa for RH hitters.
Get reps. Find someone that can hit fungos and get 100 balls 4 or 5X a week in summer. Balls can be it from middle of infield but reps matter. Also take balls in sun field to get used to playing the glare.
Above all eliminate backpeddling. If you do you get off balance and the "dance of death" will ensue where you get twisted around and almost always botch the play.
Last suggestion...learn to run without "bouncing" That is the sensation you will have if you get too much jostling as you run which will happen if you let your heels pound the ground as you run. Run on balls of your feet and learn to track ball with focus so it doesn't "bounce" as you run.