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?
If the opponents are playing standard signals, this tip is sure to screw them up.
Say the 3 is led against notrump and dummy has the A-K-5 and you have the Q-6-2. You play the king from dummy and third hand plays the 4. If you play the 6, concealing the deuce, consider the confusion you have caused: fourth hand won't know if partner has led from a four- or five-card suit (can't see the deuce) and the opening leader won't know if partner is signaling with something like Q-4-2. (can't see the deuce).
If you play the deuce at trick one, East knows that West has led from a four-card suit and West knows that partner's 4 is discouraging. For shame.