The opening lead was the ♠K and as soon as I saw dummy, I knew the field would be in 4♥ so I had to make at least the same number of tricks in NT. Here's how I analyzed it and I'd really like to know if my logic was sound.
1. I expected most declarers to win the spade lead and play a heart to the queen, hoping for ♥K to be singleton or doubleton onside. I guesstimated that picking up the ♥K was something less than 50-50. The bidding made it likely to be onside but the a priori probability of K or Kx onside vs. all other combinations was definitely less than 50-50.
2. Obviously, something good had to happen in NT: either clubs run or the ♥K is in the slot or both. Otherwise, I'm dead meat - I'm getting a zero.
3. If the ♥K is in the slot, they would be making 10 to 13 tricks, depending on the club split and if clubs not 3-2, the location of the ♦A. Otherwise they would be making 8 to 12 tricks depending...
4. If the ♥K is in the slot, I'm making 11 or 13 tricks, depending on the club split, the location of the ♦A, and the possibility of an end position. This will probably be a good result.
5. What if the ♥K is not in the slot? If I lose the heart finesse before I run the clubs, I'm dead meat. But if I run the clubs first, I'll put some pressure on them and maybe find an end position.
6. If the heart finesse wins with Kxx onside, I'll have six clubs, two hearts, and a spade for +400. Maybe a good result. Maybe not.
7. If I win the spade lead and run the clubs, I'll have a six-card end position which is worthless. But if I duck the spade lead and win the second round, I'll have a five-card end position. LHO may have to come down to the ♥Kxx, the ♦A and one spade winner. If I put him in with the ♦A, he can cash his spade but then has to lead away from the ♥K and I'll have nine tricks making +400, which is a zero unless 4♥ is going down. (I can get the same result by simply taking the heart finesse.) So how does 4♥ go down?
8. In 4♥, if the heart finesse loses to the king, they may be able to take a spade and two diamonds to go along with their heart trick. In that case, +400 will be good. If the heart finesse wins but LHO has Kxx, declarer may or may not be able to pitch a diamond on the third round of clubs. So +400 may or may not be good.
9. So it seemed like the choices were to play for nine tricks or 13 tricks.
At this point, I was unsure of what was best but was running out of time and had to do something. So I decided to play for nine tricks and ducked the first spade. LHO banged down the ♦A and I had a big, fat zero. He was looking at ♥Kx in the slot. Clubs were 3-2 and everyone in hearts made 13 tricks.
My logic seems reasonable to me but did I miss anything?