Being that most people would agree that mental training is an essential tool for success in softball especially being such a complicated game... I am curious... how and when do you practice mental training with your teams and how old are they?
All the time, every time. From start to finish, beginning at the very earliest age divisions. Ideally, as your players get older and advance through the divisions, the mental and physical part of the game will learn to collaborate with hope that game situations will slow down and allow instinct and athleticism to determine much of the outcome.
Really, softball is very easy game, that's often over-complicated by adult intervention.