If your son or daughter is playing, you should buy the Youth Baseball Coaching book if they are still 12 or under, then the Coaching Teenage and Adult Basebaball book if they continue after age 12 (about 73% do not).
And the books are not just for coaching your child. They will help players at all ages. And they will help coaches who have no child on the team. There is a list of differences between the two books here. Some relate to different rules; others, to the very different psychologies of sub-teens versus teenagers and adults.
I coached and/or played at all the levels from tee ball to semi pro and the various other adult baseball leagues (no college or pro).
Coaching Teenage and Adult Baseball by John T. Reed
$34.95 -The widespread practice format of 45 minutes of infield and 45 minutes of batting practice is a waste of time. Coaching Teenage and Adult Baseball was written by an experienced coach who tried all the stuff you’re supposed to do, found most of it did not work, then experimented...(read more)
Youth Baseball Coaching by John T. Reed
$34.95 -Most youth coaches either have no effect on their teams or actually cause them to play worse, especially in the batter’s box and on the base paths. The almost universal practice format of 45 minutes of infield and 45 minutes of batting practice is a waste of time...(read more)