You open a weak 2 in hearts with the North hand. The opps get to 4♠ and partner leads ♥8. A low heart is played from dummy and your queen holds the trick. Declarer -erroneously- put ♥2, so you know that partner has a singleton. Since this is the last time you will be on lead, you decide to cash ♥A, with partner discarding something. You have two tricks so far and it seems that you should act quickly to collect two more tricks before declarer can
(a) pitch minor losers in hand on dummy's hearts
(b) pitch minor losers in dummy on a solid minor in hand.
Basically you have two options here:
(i) You continue hearts. This might set up a spade winner for partner when he has for example ♠Q97. As declarer is aware of this trump promotion, he is likely to throw a minor loser if that can save him. For this tactic to work it seems that you need partner to have either minor ace in combination with a 'trump promotable' spade holding. Another win is a lay-out like this, where declarer no longer would have two heart discards:
(ii) You switch to a minor suit. This would work when partner has the minor king and declarer does not have tempo to get his losers pitched. A possible lay-out:
Having considered all this, it follows that partner should give us a hint with his discard as how to proceed. Is anyone familiar with some 'expert standard' in this rather specific situation? Would you follow your regular suit asking method or switch to something like: high in a suit = lead hearts/low in a suit = lead that suit?