System decisions can have enormous impact upon follow-up auctions. Sometimes, these systemic decisions are extremely subtle but may be powerful. A case-in-point recently popped up in a problem auction.
You open a minor, Responder bids 1S, you respond 1NT (11-14 balanced, say), and partner bids 2D, the GF part of 2-way checkback. What do you rebid with four hearts and three spades?
Folks may have different opinions, of course. However, when electing a partnership style, it probably pays to think through the ramifications of various decisions. Consider the impact, for example, of a decision to always support if you have support (bidding 2S with three spades and four hearts). If you do this, then a failure to bid 2S denies three-card support, right? If you do not, then a 2H call may have 2-3 spades, right?
If 2H denies three spades, and if Opener will not bid 1NT with a stiff spade, then 1D-P-1S-P-1NT-P-2D-P-2H-P-2S is an auction where Responder shows six spades and Opener shows two spades. A spade fit is established. Cuebidding may begin. Without this agreement, 2S does not establish a spade fit, Opener must bid 3S (or jump) to show spade support, and an entire level of cuebidding is lost.
In my book, I describe this auction of Checkback 2D (GF) such that Responder may set the major that Opener shows by bidding 2NT, three of the major, four of the major (signoff), a jump, or a cuebid of the other major (at the three-level). What is not discussed is when Opener rebids 2H and Responder rebids 2S.
The way I play is that Opener's first duty is to support the major first bid by Responder. Failure to do so denies three-card support. Thus, after 1minor-P-1S-P-1NT-P-2D-P-2H, Opener has denied three spades.
Once this occurs, you could agree that 2S by Responder agrees hearts and is a cuebid. This would seem to require a direct 3S after 1NT as GF and setting spades. OR, one could play that 2S after 2D promises a sixth spade and establishes trumps. It is, obviously, a choice, but at least discuss this sequence. My personal choice is for the latter -- 2S shows a sixth spade.
The parallel auction is slightly different. After 1minor-P-1H-P-1NT-P-2D-P-2H, hearts are agreed, so 2S is an unambiguous cue. However, after 1minor-P-1NT-P-2D-P-2S, Responder may need to bid 3H as natural (setting trumps). This means that the other-major non-jump cue is not a cue, but natural, when Opener's rebid is in the other major. In other words, Responder cannot bid his own first-bid suit as a cue in support of Opener's rebid of the other major.
All of this turns on a nuance, namely the answer to the first question. With four of the "other major" and three in Responder's major, what is Opener's priority after 2D?
Oh, yeah. One more problem. You also may want to consider some kind of escape plan for the 5431 problem hands. As I play it, the rebid of the minor shows this hand in two sequences.
1minor-P-1major-P-2major-P-2NT-P-3minor shows that I had 3-card support with the side stiff and a rebid problem (4-card suit would have been a reverse).
The parallel here: 1minor-P-1S-P-1NT-P-2D-P-2H-P-2S(thinks he's setting spades as trumps)-P-3C(not so quickly -- I have the 1435/1453 problem hand!). This has two impacts. First, 3C negates the trumps-uit agreement that Responder thought he had established. Second, the bypass of the non-cuebid of 3C obviously does not deny two top club honors.