Playing in a practice match on BBO with a regular partner, you pick up the following nice hand with everyone Vul, K42 AKQJ632 --- AQ7. The auction also gets very exciting before it gets near you, LHO opens 1D, partner chimes in with 3S, and RHO passes. So now what?
First off, I think you have to bid a slam on this hand, you are not sure of anything, but your hand is way too powerful to only bid game. The biggest question is, how do you get there, and what is the right slam? 6S allows your Clubs to possibly be led through, but 6H relies on not having a Heart loser with a possible Spade loser. And you do not want to write off a grand on this hand. 7 Spades to the A and out with partner gives very good play for that.
If you play exclusion key card with something like 5D, you could bid that, but that will really increase the possibility of a Club lead on the hand in Spades. You can still play in Hearts then, but will partner be able to pass that, when 5D should imply Spade support. And what will bidding 4D do for you, you pretty well know partner is going to bid 4S over that.
At the first table, this hand bid 6S over 3S, ending the auction. The hand on lead held the A of Diamonds and tried that, enabling 12 tricks to be taken when partners hand was QJT9653 4 QJ J43. An opening Club lead will defeat 6S, since Hearts are 4-1, so there are not enough quick pitches of Clubs. At the other table, the auction started the same, except the good hand only bid 4H, also ending the auction. This made 6 fairly quickly, but for a 12 IMP loss. I just strongly feel the other hand is too strong in playing strength not too insist on some kind of slam.