Develop base runners ability to read the trajectory of the pitch to determine if it will hit the dirt. Allow the defense to work on defense in the same situations.
Baseballs, catchers in gear, batting helmets
Have a complete infield including a couple of catchers in gear. Coach will pitch. Have the rest of the team with helmets on to run the bases. You don't need a hitter.
Vary the situation by changing how many runners on base. Start with a runner on first, then first and second, first and third, finally bases loaded.
Coach will throw pitches to the catcher. Every few pitches he will throw one in the dirt.
Each runner should be watching the delivery of the pitch and try to read the trajectory to determine if the pitch will be in the dirt. If the runners read that the ball will be in the dirt, he should be more aggressive taking his secondary lead anticipating that he can advance to the next base on a passed or blocked ball.
With a runner on first only, have the runners steal when they determine the ball will be in the dirt. If they read it correctly, it should be an easy steal even if the ball is blocked and/or caught on the bounce by the catcher.
When on 2nd and 3rd the runners will be aggressive in taking the secondary lead and determine if they should go or stay. The goal is for runners to get used to reading the pitch and avoiding the hesitation that often happens when a pitch bounces in the dirt.
Defensively this drill gives catchers practice at blocking pitches in the dirt with game situations. Encourage the catchers to throw the ball when runners get too far off. This is a chance for them to learn when to throw the ball and when to run someone back. It also benefits the runners as they learn how far they can get off and how to get back quickly.
Youth Coaches Note: In youth leagues where there is no leading off, this drill can still be useful in helping players get a better jump and can help defensively as well. Often young players are not prepared for the ball thrown in the dirt even though it happens many times a game. Have an assistant coach watch the runners for hesitation as they leave the base.