Counting Winners in Action - 6NT

This post talks about counting winners in NT. If you want some practice on doing that please read this post first:
Counting Winners

The reason why we count winners in NT is to determine whether or not we have enough tricks to make our contract. If we do not have enough tricks to make our contract we have to figure out a way to get more tricks! If we do have enough tricks to make our contract we try to figure out if we can make more.

So let's start. The final contract is 6NT. The opening lead is the 8♠.

Dummy:
♠AT2
♥A9
♦KQ843
♣A62

Declarer (me):
♠KQ3
♥KQ2
♦JT96
♣KQJ

Count winners -- Remember we can look at both sides to count our winners:

♠ 3 winners -- Right away I can win the A♠, the K♠ and the Q♠
♥ 3 winners -- Right away I can win the A♥, the K♥ and the Q♥
♦ 0 winners -- I can only count tricks that I will take right away. I don't have the A♦ so I do not have any winners right away.
♣ 3 winners -- Right away I can win the A♣, the K♣ and the Q♣. Even though I also have the J♣ that isn't another winner because I will have to play the J♣ when I win the A♣ in Dummy.

So right now I have 9 winners. But the final contract is 6NT. That means I have to take 12 tricks. I need to somehow develop three extra tricks for myself. Do you see a way I can do that?

That's right -- the ♦ suit. Right now I have ZERO winners in the ♦. But once I give the opponents their A♦ the rest of my ♦ will be winners. That's an extra four tricks. I don't mind giving the opponents one trick if I get four in return. Plus I am only in 6NT. I am allowed to lose one trick.

So what shall I do next?

I might as well take all my winners. That is fun! So I play off my A♠, my K♠ and my Q♠. Then I play my A♥ and my K♥ and my Q♥. Then I play my A♣, my K♣ and my Q♣. I am down to this holding:

Dummy:
♠
♥
♦KQ84
♣

Declarer (me):
♠
♥
♦JT96
♣

So now I need to play a ♦ and all the rest are winners!

WHAT!?! My RHO won their A♦ but then they didn't return a ♦! They played a ♣ instead! Since I don't have any ♣ left I had to lose a trick. I'm down 1 in my slam. Sadness. What did I do wrong?

I didn't LOSE my LOSERS FIRST.

Let's go back to the beginning. I need to play the ♦ first. I need to develop my extra winners in the ♦ suit while I still have control of all the other suits. Since I need to lose a ♦ trick (to gain four more) I must do that first thing. That way when the opponents get in with their A♦ I can win any card they return and take all my winners then.

So I will win the opening lead and right away play a ♦. If the opponents don't take their A♦ I will continue to play ♦ until they do. Then and only then will I cash all my winners. Making 6. Well done!