Here is a hand which demonstrates why you have to think carefully before making the "obvious" lead. My partner and I alight in the standard contract of 4H and North leads his singleton diamond. Since we have bid and agreed this suit, either North is someone with the IQ of a certain US President, or this is a singleton. Since North is known to be quite a decent player, everyone knew it was a singleton: the declarer; South; dummy; people at the next table, the neighbours; even
How, one of my advanced students asked me, might E/W reach a spade slam? When West opened 4S, East must have been tempted to bid on, but I agree with her that pass will probably prove right most of the time. A 4S opening bid could easily just be eight spades headed by KQJ and an outside king or queen. What else might West open? Although she has 9 playing tricks, to open 2D (as those who play Weak 2s in the major suits must) gives the opposition a chance to enter the auction.