At Notrump, the best defender's weapon is the choice of the suit to lead!
You must try to set your own long suit - I mean your own team's long suit, before declarer can freely run his master cards.
This hand has been played yesterday in a local tourney, where 75% of South players lazily lead the
♦ Ace, thus allowing declarer to score 600.
If you know your history, you've been taught to lead 4th best of your longest suit at Notrump.
Why? Because its the best way to set that suit!
And this simple lesson makes a big difference! Look:
If you lead the
♦ Ace, declarer will eventually make his
♦ Queen and try the
♥ finesse, playing the Jack from his hand.
Your partner will make his
♥ Queen, but alas, he's got no more
♦ to lead back for you.
As a result, declarer will make 3 ♠ + 4
♥ + 1
♦ + 1 ♣ = 9 tricks.
What do you prefer: fulfill your ego playing your master Ace and King, or set the contract?