Wait until the CPU has a runner on third base. Then,
hold Left on the Joystick, hold [Shift],
and press Fire.
Hit the ball out of the park:
Stand in the extreme top corner while batting to have
a chance to hit the ball out of the stadium.
Easy CPU pitchers:
Press P to enter the substitution screen while
the CPU is pitching. The game will allow you to switch the current
pitcher for a much weaker player.