The Weak No Trump (12-14)
Introduction: In standard 1NT shows 15-17. With this range generally the
partnership is safe at 1NT or 2 of a suit. However the 1NT opening does not come up all that often. In any case, most people try to
disrupt the partnership's bidding after opening 1NT. For the most part such disruptions are successful since rarely is the hand theirs
when an opponent's hand holds 15-17.
On the flip side of the standard 1NT is the weak no trump showing 12-14 (a very good 11 could also be opened). Although it is not as "safe" as the strong 1NT, the weak no trump has some merits:
The weak no trump hand:
It is a balanced hand of 12-14 hcp. It denies a void, singleton, and a 5 card major. A good 11 point hand could also be opened 1NT if it has a good 2 1/2 tricks. 1NT could also be opened on a bad 15 (ie some points are duplicated--- like QJ doubleton).
Responder generally knows where the hand should be played. With 0-6 hcp, responder should usually run to a suit contract--- unless responder is also balanced--- in that case he may decide to just have partner "stick it out" at 1NT. With 7-10 responder knows that 1NT is safe and usually does not run unless he has a 5 card
major. With 11 responder invites game (except in a minor, of course). With 12+ responder knows game is there and should make sure the partnership is there.
I prefer to use 4 suit transfers myself, but any other response structure is fine.