Rules for the second player to a trick
Second player - plays low
There is saying in bridge 'second person to play to a trick should play low' and generally that is correct. Usually it is better not to win the trick but to duck in order to allow your partner who will play 4th to the trick a chance to win it. This is generally used with reference to the defense in a game of bridge but declarer can also benefit from using it as well.
Against a NoTrump contract look what happens if the second player Dummy to the opening lead plays high on the opening lead, Declarer will lose all 4 Club tricks