We're playing in a Pairs game (matchpoints), I'm sitting South. Both sides are vulnerable. How do you like the NS bidding?
(1) First of all, 2NT is just awful. True, I don't have a bid that describes this well and obviously can't pass with 12 HCP facing a first seat opening bid. So I just thought this lie (about the spade stopper) is as good as any. I should have thought about the likely consequences. If we have a game on, partner is probably just going to raise me to 3NT, and then I have the spade lead to look forward to. Especially funny if partner puts down Kx in spades and 3NT from his side would have been cold.
The right bid is 2S. Partner would normally expect 4+ card diamond support, but we do play that a cuebid could also be a strong hand that doesn't know what else to bid. Are there any likely disasters coming after this bid? Not at all: On a bad day, partner might blast to 5D, expecting 4 diamonds in my hand, but even then I'm putting down solid values.
(2) After partner's 5D bid, what is the situation? EW clearly have their bidding shoes on, but even so you must give them credit for 9 spades, giving partner a void in spades. In other words, partner's shape is 0-5-6-2 at least. How can slam not be on opposite this and with three prime cards (A, AK) and decent diamond support. Pull the 6D card out of the box!
(3) One round previously, what was the situation after partner's surprising 4H bid? This bid would clearly be absurd on just 4 hearts. You have all the information at this point already - make it 6D!
(4) Now what does this say about partner's 5D bid? It's not giving me additional information, I already knew after his 4H that he's 5-6 in H/D (OK, I wasn't listening carefully, but partner should trust me anyway). More to the point, it takes away the option to double 4S, which, from N's point of view, may very well be our only plus score at this point (remember, N should place some of my points in spades, where they are wasted). North should pass here and can safely do so since this pass is clearly forcing.
Just some basic principles (think ahead, visualize, don't say it twice), but you do need to keep a clear head to get it right at the table.
By the way, the scores on this board for NS were 1460, 720, 710, 710, 640 (us), 640 (someone else played in 5D). This is easy to explain:
(1) It's not mandatory for E to overcall. An uncontested auction would start with 1D-1S. This is disappointing for N. Do you bid 2H anyway? I think this would be a really bad idea. We play a reverse shows 16+ HCP, so you're telling a big lie. Also, S seems to have wasted values in spades and the whole deal seems a misfit. Time to get real with 2D. I then have an easy 3NT call.
My 1S bid hopefully talks the opponents out of a spade lead, so 3NT makes 7 if you find the Q of hearts, and that's good for +720.
(2) In the above auction, it sure doesn't feel good in N's seat to pull the second card out of the bidding box and his 5 card major is still a well kept secret. I guess some experts will tell you that for such reasons, you should open 1H instead (I don't like it, there is potential for a slam, and you want to describe your hand accurately). I think I'd call my hand a 3 card limit raise then, which we bid by starting with a forcing 1NT and jumping to 3H then: 1H-1NT-2D-3H. I think it's not terrible to call it quits with the N hand after trying 3S-4C-4D-4H (club losers a major concern if partner has only 3 trumps). 4H makes 7 or +710.
Finally, let's say you do bid your way to 6H and make 7: that's +1460.
One more thing: note how EW's interference actually makes it easier for us to reach the slam.
(Sorry for the long post.)