Source: http://www.michaelslawrence.com/
Both Sides Vulnerable; West Deals
Salida: 
2
There are many situations where the correct play goes against the grain. This hand includes such a situation. My experience suggests it would be mishandled by a huge majority of players. South was playing 15-17 notrumps so had to start with one club and then rebid two no trump. North scratched up a marginal but correct raise to game.
West’s heart lead did not put declarer in any danger. Declarer had considerable time to establish either clubs or spades to get nine tricks.
He chose to work on spades because they were stronger than the clubs. South, therefore, won the heart lead and played ace and another spade. West played low and declarer played the jack losing to the queen. The heart return was won in dummy and another spade played in hopes they were 3-3.
They weren’t, and declarer ended up with only seven tricks. Declarer was happy to see clubs were 4-2 meaning he couldn’t set them up either but his comfort was misjudged. He should have made his contract.
Do you see how?
When declarer led the second round of spades he should have DUCKED in dummy which would have succeeded if East had started with any three spades or if he had a doubleton king or queen. This play would lose if West had ducked with both honors but that would require that West had both spade honors and then in fact did not play one of them when declarer led the suit. Without going into the exact details of this suit combination, it is true that there are more doubleton honors that East can have than small doubletons that East can have. If you add into this that most defenders in the West seat would win the trick if they had the king and queen. Human nature. All in all, the correct play in this suit is to play and ace and then a low one from both hands.
NOTE that if the opponents bid and you knew from the bidding that West had most of the high card points, then you might choose to go up with the jack or ten, but in general, that play is against the odds. Learn this combination. You will see it at the table soon enough. I promise.