"As I've said before," said Spock, "killing partner is not necessary or helpful. And it ruins the baize..."
"But, but, but.. " said the very large Klingon, dropping his partner, "Twice he didn't continue the suit he led at trick one. We coulda had them down twice. That is not acceptable on my planet. He needs to know my attitude to failure, know what I'm saying?"
"I think he'd rather know your attitude to the suit led, wouldn't he?"
"Huh? Are you implying it's all my fault?"
"Yes that's right I am indeed. You could have an agreement that the card played by opening leader's partner, when not forced to play high, can be an ATTITUDE signal. ie whether or not you want partner to continue that suit when they can. Say partner leads QS against 3NT and you hold 109653 in the suit. If Dummy (or Declarer) wins the trick, now your card can be attitude showing. The 9 will encourage partner to continue the suit later, and the 3 will be discouraging. Now partner knows what to do. Simple huh?"
"Hmm maybe. But what if you only have one valuable high card to play to encourage with? That's a problem, no?"
"It is indeed. Very well spotted. This is why a lot of players actually play what's called REVERSE ATTITUDE. ie a LOW card is encouraging, the high one discouraging (Hi hate, Lo like...) In the previous example the 3 would be encouraging. You will of course have to watch every single card partner plays, now won't you? Working out what Declarer has; where's their weakness? In fact, do this anyway: all the time. Otherwise you're only playing half the game."