Today’s hand comes from a very good book on card play called «Adventures in Card Play» by Geza Ottlik and Hugh Kelsey. Unfortunately, the book is of a very advanced nature and only for a handful of bridge players. 
South found himself in four spades after an aggressive auction. He also found himself facing an unfavorable lead of the king of hearts.
He ducked once on general principles. Sometimes, the opening leader will shift, but West continued with the queen of the suit.
SOUTH TOOK his ace and led the queen of spades. West followed low and South thought for some time before rising with dummy’s ace.
Then he led dummy’s queen of diamonds. East covered. South took his ace, led the four of diamonds back to dummy’s 10, returned to his hand with the ace of clubs and discarded dummy’s last heart on the jack of diamonds.
LATER ON, HE LOST one club and the king of spades, but he had his 10 tricks. Don’t think that we are showing result play.
The result was favorable, but the play was almost automatic for a real expert. The point is that the contract was not going to make it if the diamond finesse lost.
With the diamond finesse right, a successful spade finesse would produce an overtrick. With the diamond finesse wrong, it would merely mean going down one instead of two.