The fundamental principle of standard American bidding is a new suit at the two-level shows 10 HCP’s and promises a rebid. This applies in competitive bidding as well.
When the person first bids one No Trump over partner’s opening or makes a negative double over opponent’s overcall and follows with a new suit, the new suit is just to play and shows less than 10 points.
The bidding: This is a hand that occurred at the Creston team game. North opens one diamond, and East takes the one-level away with a two-club overcall.
If South makes a call of two spades, that would show 10+ high card points, and if he followed it by three hearts, that would be forcing to game. Therefore, he makes a negative double. Partner rebids diamonds, and East persists with clubs. South passes, and North rebids diamonds. South bids three spades, and it passes out.
West should actually bid four clubs because he has three useful controls, an ace and a king. East has bid to three clubs all on his own, so West’s singleton club is not a problem. Perhaps West should raise to five, but East will certainly do so.
Five clubs goes down on a club lead, but who can blame South for leading a diamond, a suit rebid by his partner.
If declarer makes his contract because a player did not lead his partner’s suit, that would be bad for partnership harmony. East was actually bidding as if he had no diamonds, but with a singleton diamond himself, South found that hard to believe and led his diamond.
The Lead: The nine of diamonds, the Ace of Spades and the ten of clubs are all candidates for an opening lead. For partnership moral and since no other lead seemed best, West led the ten of clubs.
The play: East wins the opening lead with the Jack of clubs and plays a small club for partner to ruff to get a diamond return. A high club spot would ask for a heart return. Partner ruffs with the Ace and obliges with a diamond return.
West gets a small ruff and later his King of trump. Declarer loses three spades, one heart and a club for down one.
Results: Three spades down one for -100. At the other table, five clubs makes for +400 and a 300 point swing.