Oscar Wilde said, “It is only an auctioneer who can equally and impartially admire all schools of art.”
It is only a successful bridge player who listens carefully to the auction and uses the information to guide his defense.
In this example, how should West hope to defeat four spades after he leads the club ace?
North’s sequence, Stayman followed by the jump to three no-trump over two hearts, guaranteed four spades. So South corrected to four spades. Note that the defenders could have taken five immediate club tricks against three no-trump.
Many inexperienced defenders cannot wait to cash winners. They would take the club king about one nanosecond after winning the first trick with the ace. Then they would look around to decide what to do next — too late. Their best move would be to feign a sudden illness and to flee the premises!
When dummy comes down with three hearts, West should realize that his partner has a singleton. So, there are two ways to win by shifting to a heart at trick two: Partner might have either the singleton heart ace or the spade ace.
As you can see, this defense defeats the contract. East wins the first (or second) round of trumps, puts West on lead with his carefully preserved club king, and receives the contract-killing heart ruff.
As the bidding progresses, mentally log what information it imparts. And slow down your play: there are no prizes — except booby — for speed.