[arepo24]

If my partner plays an A in a suit that has not been played and I have the Q6 of that suit, do I play the Q to show a doubleton or do I play the 6?

[Stephen Tu]

On opening lead, you play the 6. The standard signalling convention is that playing the Q shows either the singleton Q, or that you have both the Q and J of the suit. This allows partner to underlead to your J for a shift to another suit through declarer, which might be critical.

So you have to play the 6 since otherwise you may find partner underleading to your non-existent J and declarer gets an undeserved trick.

Now if the J is in dummy, so partner knows not to underlead, you might play the Q if you really want king and a ruff, but this depends on the rest of the hand, you might not want to waste the Q, hope to score both honors without disturbing your trump holding or setting up dummy's J.

Also note that for leads breaking a new suit in the *middle* of a hand, after trick one, even if your agreement at trick 1 is to lead A from AKx(x), you really should play K from AK holdings, with the ace *denying* the K. This is because banging down an ace without holding the king in the middle of the hand is far more often the right play vs on opening lead (ace from empty on opening lead is usually unattractive because you capture air; but after you see dummy you may see no honors on your right to capture), and you want to get an accurate signal in these cases.