Time the play to make a contract

Hesiod, an ancient Greek poet, said, "Observe due measure, for right timing is in all things the most important factor."

Right on! Many things in life require good timing: Meeting a potential spouse, a golf swing, music, and making or breaking a bridge contract.

In bridge, the order in which the cards are played often makes the difference between success and failure - as in today's deal. How should South time four spades after West leads the heart king?