Instructions
Dash toward the ball after it gets hit. Depending on which controller configuration you're using, you may need to shake the Wiimote back and forth, press the 1 button, or just use the Nunchuk's joystick in order to dash.
Aim Yoshi's face toward the ball cursor. If the ball has been popped particularly high, move Yoshi into a position just outside of the ball cursor. His tongue is just about the length of his body, and as long as the ball lands on any part of his tongue, he will catch the ball.
Press the special move button or button combination about one second after you see the ball on your screen. Depending on your controller configuration, you may need to press the A button, the 2 button or the A button with the Nunchuk joystick to execute the Tongue Catch.