This hand is filled with lessons. I will try to keep them simple.
Lesson one: The Opening Lead. It is very rare that it is wrong to lead a singleton. The hard part is getting partner to recognize when the card led is a singleton. Here is a simple rule: When both partners have agreed on a suit and then the opening leader starts off with a different suit, it is very likely to be a singleton.
Lesson two: Declarer calls for the ace of diamonds from the dummy - there is no reason to give away the position of the king. He then calls for a small club to his ace. The five of spades is next. West doesn't hesitate. He plays the ace of spades. It is very much the norm that second hand plays low. The exception is when it is right to win the trick. Think ahead. If West plays low the trick will be won in dummy with the king and the only trump that West has to work with is the ace, which he will always win anyway. So when you are trying to score a ruffing trick, try to keep a small trump in your hand for that purpose.
Lesson three: West has to find a way into his partner's hand so that a diamond can be returned while he still has a trump. Does partner hold the ace of hearts? Maybe. Thats the best answer you can come up with. If he holds that card, you want him to win it on the first lead of the heart suit and return a diamond. You don't know if declarer has one or two hearts, if he has any, so leading the king of hearts won't do you any good. Partner will duck and while you win that trick, declarer may be able to trump the second lead of the suit. To cater to all of the possibilities, lead the queen of hearts. If partner has the ace he will win it to keep declarer from winning his possible singleton king. Also, he is much more likely to return a diamond. A second heart will just not look right.
Partner does win the ace and does return a diamond. You ruff and cash the king of hearts defeating an otherwise unbeatable contract.
To accomplish all of this is no small task. It requires
planning and intelligence by each partner in the defense. There
is no such thing as an "automatic" play. Stay alert and be a
good partner - your scores will improve.
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