Starts with the coaches' and parents' attitudes. The players will key off this to a great extent.
It is not the biggest tournament of their lives. It is another baseball game. And you don't play tournaments. You play a game. One game at a time.
They have been in games before, they will be in them again.
Relax, have fun. Execute the same fundamentals they have been executing all year long.
And I have seen coaches who change their game strategies in the "big" tournaments. Seldom works. "Dance with the one that brung you"...