When your pitcher has a no-hitter going, you must not say anything to him about it. If he has a perfect game going, he must be made to sit at the end of the bench and ignored completely.

If you are on the opposite team, you must constantly tell him. Yell, "Hey you're pitching well - a no-hitter even." as you come to bat. When the opposing pitcher bats, the catcher should encourage him to keep up the no-hitter.