OPENING BID OF ONE CLUB: Artificial: does not indicate a club suit. Strong: Promises at least 17 points in high cards or powerful distribution. Forcing: Partner must respond.
RESPONSES are artificial "stepladder" bids (similar to responses to Blackwood four no trump) and show the number of "controls": king equals one control; ace equals two controls. Thus: One diamond shows none; one heart, 1; one spade, 2; one no trump, 3; two clubs, 4; two diamonds, 5. With 6 or more, the response is two no trump. The two-heart and two-spade responses are natural; they indicate a real suit without any controls.
OPENING BID OF ONE IN ANY OTHER SUIT: Normal bid, indicating 12-17 points and at least four cards in the suit named.
RESPONSES: Responder's first bid need not necessarily indicate his real suit, especially if his second bid names a suit that is higher-ranking. This second suit, however, must be playable.
OPENING BID OF ONE NO TRUMP: Shows a normal 12-17 point hand with clubs the only long suit.
RESPONSE of two clubs announces a weak hand, including at least two cards in clubs.
OPENING BID OF TWO CLUBS: Same strength as above, but showing at least five clubs and may include a second biddable suit.
RESPONSE of two diamonds is weak.
ALL OTHER OPENING SUIT TWO-BIDS: Usually a weakish two-suiter (12-13 points).
RESPONSE of two no trump asks for second suit to be shown.