Much of the complexity in bridge arises from the difficulty of arriving at a good final contract in the auction. This is a difficult problem: the two players in a partnership must try to communicate sufficient information about their hands to arrive at a makeable contract, but the information they can exchange is restricted—information may be passed only by the calls made and later by the cards played, not by other means; in addition, the agreed-upon meaning of each call and play must be available to the opponents. Since a partnership that has freedom to bid gradually at leisure can exchange more information, and since a partnership that can interfere with the opponents' bidding (as by raising the bidding level rapidly) can cause difficulties for their opponents, bidding systems are both informational and strategic. It is this mixture of information exchange and evaluation, deduction, and tactics that is at the heart of bidding in bridge. A number of basic rules of thumb in bridge bidding and play are summarized as bridge maxims. A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination. Compare this to heuristic, a similar concept used in mathematical discourse, psychology, and computer science, particularly in algorithm design. The exact origin of the phrase is uncertain. The earliest citation comes from J. Durham’s Heaven upon Earth, 1685, ii. 217: "Many profest Christians are like to foolish builders, who build by gu ss, and by rule of thumb."[1] The phrase also exists in other languages, for example Swedish tumregel, Norwegian and Danish tommelfingerregel, sometimes in the variant "rule of fist", for example Finnish nyrkkisaanto, German Faustregel or Dutch vuistregel, as well as in Turkish parmak hesab? (rule of finger) and in Persian "? ," which is translated as finger's tip rule. This suggests that it has some antiquity, and does not originate in specifically English-language culture. Bidding If you have a choice of reasonable bids and one of them is 3NT, then bid it. Known as "Hamman's Law"; devised by Bob Hamman and published among other places in English Bridge, June 2006, page 19. Prefer majors to minors. Bid a major suit before a minor suit. They can overbid opponents at the same level, and score higher. Prefer length to strength. A long suit, even if weaker, is often ultimately more powerful and desirable as a contract, than a short suit, however good, because long trumps will usually make tricks in the end, and they allow a greater level of control during the game. With a misfit bid cautiously; with a good fit be bold. Avoids chasing a poor contract with a misfit, but enables a surprisingly high contract with a good fit. [edit]Card play [edit]Leads, signals and discards If in doubt, lead a spade. This applies to NT contracts and works on the assumption that declarer or dummy would likely bid spades if they had them. (Because it is axiomatic to consider a major suit fit if one exists, before settling on no trumps, and spades as the highest ranked suit are the suit which would have been easiest to bid had a fit existed.)