Playing online, we used a precision auction to investigate slam and stop at 5S:
The 1C was Precision, showing 16+ points. Partner's 1NT is natural, showing 8-11 points. I showed my 5 card suit and he raised with 3-card support. 4C is a control-bid as is 4H. This denies a diamond control, so I know that partner does not have the Ace of diamonds. Should I explore slam?
This is where Culbertson's rule comes in handy. If you can come up with a minimum hand consistent with the bidding where slam is cold, then explore slam. What does it need for slam to be cold? Partner needs the king of spades, Ace of hearts, QJ of diamonds and KJ of clubs. That is 14 points. Partner probably has 10-11. So, what should I do? I should sign off in 4S.
But ... mistake #1, I bid Roman-Keycard Blackwood. Partner showed 1 key card with 5D. East now doubled for the lead. That is mistake #2 -- he should not have doubled (you will see why shortly). I bid 5S which gets passed out.
West, following his partner's lead-directing double, leads the 10 of diamonds. This is mistake #3. What should I play from dummy?
The 10 would normally deny the Jack, so it clear to put up the Queen. When East goes up, I can now finesse his Jack with K-7. Watch the spots! Unfortunately, I failed to do that. I woodenly played low from the board -- mistake #4. The right play is why East was wrong to double -- left to my own devices, I can not play the diamonds for only one loser.
But East didn't make a mistake now. He correctly ducked the 10 diamond lead and my 5S contract was toast. I had made the last mistake on this hand, in not going up with the Queen of diamonds.
Playing in a sectional Swiss over the weekend, there was board after board of this type of play-of-the-hand mistakes. Mostly, my mistakes didn't cost us imps, but they prevented us from gaining useful imps. We ended up losing matches when the opponents managed to find and bid against-the-odds slams and games. We would gain 1-2 imps a board and then lose it all on the freak hand. Gaining 2-3 imps a board, which is what we should have been doing sans card play issues, would have gotten us a better finish.
As it was, though, losing our matches early allowed us to blitz back through the soft-underbelly of the field, and finish 3rd in B. Still, it felt ridiculous to be playing a C team in the last game of the Open Swiss and finding that we were getting a double game swing on this hand:
You could argue over whether you should double or bid 3D or 2NT with my hand (what would you do?). But you have got to do something ... At the other table, our teammates preempted a level higher (7-card suit, 6 losers whichever way you look at it) and the auction went: