I am a firm believer in using the 1NT as an obstructive bid, forcing opponents to enter the auction at the 2 level. However, bidding 1NT with a flat hand containing 1 or 2 four card majors is a no-no.
The 1NT I force upon my partners ( on pain of death ) promises a 5 card minor, and at least one major with a 3 card suit. Acceptable distributions within the 12-14 point range are 3-3-5-2, 3-3-2-5. 3-2-5-2 and 2-3-5-2. Any other distribution/shape requires opening a suit at the one level.
As for responses .....well nothing could be easier. 2C says no game interest, pass if you have clubs or covert to 2D. 2D is the staymanic response which tells partner to bid his lowest 3 card major ( and await developments, if any ). 2H/2S promises 5 in the major, game forcing. 2NT promises a balanced 11-12 with no more than 4 in a major. Simple heh ?
And what's so good about it ? Well firstly, partner with a weakish hand and a 4 card major knows there is no point in trying to find a non-existent 4-4 fit. Partner also knows that with 5 in a major he is well placed to play at the 2 level in either a 5-3 or 5-2 fit. 1NT doubled is less likely to be damaging if there is a 5 card minor suit in which the NT bidder can escape into.
Indeed, the beauty of the bid enables one to open a prepare 1C to show a hand with one, possibly two, 4 card majors, where a 1D reply is the enquiry bid ( to which there are a multitude of informative responses ). Moreover, opponents are less likely make a frisky overcall at the one level with a flimsy 5 card major of their own......knowing you might have that suit. As for all other one-level opening bids ( 1H/S ) : these will show a five card suit or better. 1D will either show a 5 card or better diamond suit, containing a possible singleton or void, or a flat hand with 4-4 in the minors 15+ points. With an opening hand in clubs, which can't be opened 1NT, then it is a case of waiting to bid at the next opportunity if there is one. So the only problem hand is a flat 12-14 with 4-4 in the minors, which requires a disciplined pass on the first round of bidding. Some experts have had the gall to tell me that this Bigot-Johnson 1NT is seriously flawed. Well, my boys are all using it to maximum effect pulling in tops left, right and centre. Never argue with success is what I say to them.
( Footnote: Any comments will be gladly received and carefully scrutinised. Criticisms will be tolerated to some degee, but constructive advice regarding refinements will be much more appreciated. )