In general, the younger the player the more instruction you give them during the game. As they get older and more experienced playing the game, less instruction is better during the game. When they are young, 8U & 10U, the other coaches and I talk to them all the time. Frequently when we play other teams you'll see for example, baserunners are not set-up and leading off correctly; they try to catch the ball with a forehand catch and should be using a backhand to field it; fielders are not in "softball ready" position; batters are too far back or too far forward in the box; etc and no coach is correcting the players. If you are not correcting them during the game, when are you going to correct them, at practice two days later?
However, as starsnuffer points out, you better make sure you have something important to say before you say it.
However, as starsnuffer points out, you better make sure you have something important to say before you say it.