Source: www.qldbridge.com 
If you want to improve your scores in duplicate, especially in pairs, it’s important to have a firm grasp on competitive bidding strategies. This means, of course, serious discussion with your partner about the tools you will use in this ongoing battle. Most pairs have some method of competing when the opponents open 1NT, be it the 15-17 variety or a socalled “weak” 1NT. The latter includes many ranges, from 10-12 to 13-15. You and partner must decide which of the ranges represents “weak” and which include “strong.” It’s not essential, but many pairs play different methods depending on whether the 1NT opener is weak or strong.
The latest edition of the Official Encyclopaedia of Bridge lists no fewer than two dozen schemes for competing against 1NT. No doubt there are many more in service around the world. Two of the most popular conventions for mixing it up with both strong and weak 1NT openers will be covered on this page tomorrow. Before getting into the details, it’s important to answer this question:
What kind of hand do I need to get involved?
As a general guideline, I usually recommend the formula devised by Mel Colchamiro, who wrote a column for the Bridge Bulletin for several years. Colchamiro calls his formula the Rule of Eight. It works this way: If you are thinking about entering the auction to show a two-suited hand after a 1NT opener, use this formula: count the number of cards in your two long suits and subtract the number of losers in your hand. If the answer is one or zero, pass. If the answer is two or higher, use your system.
For this purpose, a “loser” is a missing ace, king or queen in a suit of three or more cards. A doubleton cannot have more than two losers, a singleton no more than one. No suit can have more than three losers. For example: A J 10 9 5 K Q 7 3 8 6 4 3
The spade suit has two losers (missing the king and queen), the heart suit one (missing the ace). There are four losers in the minors. Total losers: seven. Now subtract seven from nine (the number of cards in the majors) for a sum of two. Use whatever bid you have to show the majors. Change one of the spades to a club or a diamond and you should pass. Using two as the minimum benchmark for competing, the rule achieves the status of eight with the stipulation that the hand must have at least 6 HCP.
Another point for discussion with partner: Do you use the same method for direct action over a 1NT and in the passout seat? Some partnerships vary the systems, but it’s probably best to keep it simple, at least starting out. The less you have to remember the more effective you will be. Be careful about entering the auction at unfavourable vulnerability (you are, they aren’t). If you and partner can’t find a fit, the opponents may not have to double to get a good result.
Whatever your method of showing a long suit, try to avoid doing so with only five. Mike Lawrence, one of the all-time great writers, recommends passing with any 5-3-3-2 hand no matter the HCP. His theory is that if you can make something with that hand, you’re probably going to defeat 1NT. Don’t risk losing your plus score. With 5-4-2-2 shape, call it a two-suiter. Wait for the six-bagger, especially vulnerable. As your hand gets more shapely, the danger in competing is reduced.