Not a coach, but the biggest thing I'd offer is to know exactly how the kids have been trained to run. Very frustrating for a kid to be taught one thing all week then have something else expected during a game.
Don't teach stupid aggression, be smart and don't expect players to miss throws and tags
Being a good base runner is about ARR. Anticipate-Read-React
Runners should always "follow ball back "to the pitcher
Look for lazy catchers , know where the strong arms are