Surely a player of your bridge skills is familiar with most or all of the following tips you are about to read. But is your partner?
When there is a short side suit in dummy and declarer draws all of dummy's trumps, the inference is that declarer doesn't have any losers in that suit to ruff. Translation: It is safe to discard that suit.
When discarding, keep length parity with the dummy. If dummy has four cards in a suit (A-K-Q-8), and you have four cards (9-4-3-2) one of which (the 9) could conceivably take a trick, be careful about discarding from that suit. Be very careful! Don't!