Baseball coaches can use a wall to teach correct throwing and hitting mechanics. The same drills could be used with a fence instead of a wall.
Teaching youth baseball hitting is more 'trouble shooting' than emphasizing one particular theory or approach. In order to prevent young hitters from stepping out during the stride, set a bucket to the left of a right-handed hitter's front foot or to the right of a left-handed hitter's front foot.
The batting tee is often an under-utilized teaching tool.
For youth baseball hitters who have a dominant bottom hand, set two whiffle balls on top of each other on a batting tee and have the player hit the top ball. This drill emphasizes top hand hitting.
A youth baseball hitting drill combining short toss and tee work can correct stepping in the bucket and/or opening the front hip too early. Throwing short toss inside and forcing the hitter to then hit the ball off the tee on the outside corner forces the hitter to utilize the same lower body mechanics regardless of pitch location.
Hitting badminton birdies is a great youth baseball drill to help hitters stay back and rotate through the baseball.
Youth baseball coaches can whiffle balls during batting practice to allow more hitters to swing at the same time. The more swings a hitter gets in practice, the better they will be in the game.
The batting tee is a great tool for youth baseball hitters who struggle with getting the bat on the proper plane. Youth baseball coaches should adjust the tee up for those who uppercut. For hitters who severely chop down on the ball, place the tee at their knees