Source: The Morning Record – 19 Sep 1964
During the action you count your points and add them to the, points shown by your partner’s bids. The total tells you how high your side can afford to bid. Keep counting after the auction has ended: you may find out, how high to play.
South dealer Neither side vulnerable
Opening lead — 
6
West opened the six of hearts and declarer correctly played low from dummy. East played, well…What did he play?
East counted 12 points in the dummy and 11 points in his own hand. Since the deck contains only 40 points, South and West had 17 points between them. South needed 16 points for his bid, so West could have 1 point at most.
East next used the Rule of Eleven, subtracting the opening lead from 11. The remainder, five, told him that dummy, East and South held five cards higher than the six of hearts. Dummy held two of those five cards, and East held two: so South could have only one heart higher than the six. The counting process took only a few seconds because East was used to it.
East then knew that South’s hearts were headed by the queen and West’s by the jack. East was ready for his first play
DRIVES OUT QUEEN
East played the ten of hearts, at the first trick, and South had to win with the queen for fear of not getting a second heart trick if he failed to take it. Declarer next led the ten of diamonds, hoping to steal one trick, but East took the ace of diamonds at once and shot back the king of hearts to dummy’s ace.
South could get only eight tricks outside of clubs. As soon as declarer led clubs East took the ace and led his last heart to give West three heart tricks. Down one.
The counting and planning were necessary to defeat the contract. If East wins the first trick with the king of hearts. South still gets two heart tricks, but the defenders get only one. South makes ten tricks instead of only eight. Make it a habit to count declarer’s points when you are, defending. You can then count your partner’s probable points and can defend as though all the cards were face up on the table.