I am West, defending a no trump contract. (No bids by our side, no other bids than NT by the opponents.)
We're down to the last few cards, and I have two suits, call them diamonds and clubs, like this:
(d) Kx (c) Qxx
I am guarding two suits, and when South leads a third suit, e.g. a heart, I will likely be squeezed because I have two "secondary" (non top honors) that need to be protected by x cards.
If I knew that partner had e.g. Qx of diamonds, I could "transfer control." of that suit by discarding K, and then x, while protecting the club suit. If I knew partner had Jxx of clubs, I could discard my Qxx of clubs and protect diamonds.
How do I know whether (and in which suit) I can transfer control to partner in this fashion? What should I have been doing/looking for in earlier play to help make this decision?