Responder's rebids after her first response is 1NT
To recap: your partner has opened 1♥ or 1♠ and you have responded with 1NT, showing 6 to 9 (or a bad 10) points with nine or so losers. You have limited the strength of your hand, so your partner has been able to make a pretty good judgement of the strength of the partnership's hands (in terms of points and possibly losers).
If she PASSes, then the partnership will be playing in 1NT. It's possible that you have a suit which is not stopped (in rare, very bad situations you might be missing stoppers in two suits.) But she's made the best decision she could given that all she knew was that you didn't have a fit for the major suit she opened and you have 6 to 9 points. Thank her for stopping the bidding at a low level and do your best to make the contract.
If she bids something else, then you have to look at what you know about the partnership's hands and make a decision or two. Sometimes these decisions will be choices between "the pit and the pendulum" but make the best decision you can. Some examples in this lesson will hopefully help you with some of these decisions.
Opener has bid a suit at the 2-level
but has not reversed
When she has bid another suit but not reversed after your 1NT response, she's saying that she has an unbalanced hand (not flat) which couldn't reverse (for whatever reason). She has between 13 and 18 points and is asking you to choose which of her suits you'd like the partnership to play in. Most of the time you will choose the suit in which the partnership has the best possible fit. If you have a suit of your own which is quite strong, you can bid it instead. But this will be uncommon since you have only 6 to 9 points.
If your partner surprises you by bidding a suit and you discover the partnership has a fit, add those support points and see what you think the partnership has! Sometimes it's enough to jump right to game.
Finally, you can invite game in some situations when your hand has been improved by her rebid. This will only happen when a fit has been found.
♠J2 ♥K8732 ♦QJ7 ♣983
She opens 1♠ and you have had to make the unattractive response of 1NT. She then bids 2♣. You know that the partnership doesn't have enough for game, so you want to get out in the safest possible contract. She has shown five spades or more and four clubs (sometimes more, but most of the time it will be a four-card suit). So you don't think the partnership has a good fit in either suit. You'd like to suggest hearts, but your heart suit doesn't have many high cards (sometimes called a "ragged" suit). Since it's just slightly possible for her to have six spades, you should prefer spades and bid 2♠. This does not tell her that you have a fit for spades. If you had such a fit, you would have made a bid different from 1NT. It just tells her that you like spades a little better than clubs.
♠J ♥KT8532 ♦QT64 ♣73
She opens 1♠ and you responded 1NT. Then she bid 2♣. Ugh! You don't like either of her suits at all. Your hearts, although long, are pretty ragged. You probably think that no bid seems to work here. If that's what you're thinking, you're absolutely right. It's probably best to bid 2♠ and hope that your ♠J can be of some use to her. It's an ugly choice, but you're doing the best that you can. If you prefer to bid 2♥, I can't really blame you, but your partner will expect you to have stronger hearts (so if she has a singleton or void she can PASS). The partnership hands are what is known as a "misfit". With misfit hands, you have to stop early and it's possible that you have to stop in a contract which might not be very safe.
Suppose you have the same hand, but the bidding goes (with opponents PASSing) 1♠ by your partner, 1NT by you and 2♥ by your partner. The partnership does have a major suit fit (and what a fit it is!) You can add support points bringing your total up to 10 points. You have seven losers which suggests that game is possible (remember that her opening bid means that she has seven or fewer losers and her minimum rebid has suggested that she has seven). You don't have quite enough to jump directly to game, but you can invite game by bidding 3♥. This tells her about the heart fit and the fact that your hand has improved enough to invite game. She can then look at her hand (adding support points) and decide if game is possible (she'll bid 4♥) or game isn't very likely (she'll PASS).
♠T32 ♥73 ♦KQJ872 ♣82
She opens 1♥ and you respond 1NT. She then bids 2♣. Your best choice here is probably 2♦ (although I wouldn't necessarily bicker with a 2♥ "preference"). You have a long suit which is pretty strong (given that you have 6 to 9 points).
♠876 ♥T9 ♦KQJ7 ♣8654
She opens 1♥, you respond 1NT, and she rebids 2♣. This one is somewhat close, but PASS will probably work out well here. [NOTE: in special tournament bridge called duplicate bridge, 2♥ might be better since making this contract scores more points than making a 2♣ contract. However, we're just looking at bridge in general right now.] Clubs might be better because your partner (who has five hearts since she opened them) can ruff some of her losing hearts using your low clubs if clubs are trumps.
Opener has bid 2 or 3 NoTrump
After she bids 2 NoTrump, you know that she is inviting game in NoTrump. You need the "top" of the 1NT response range to accept game. That is, you need 8 or 9 points to accept the game invitation.
At this point, you need to decide if your hand is for NoTrump (flat distribution) or your hand is better for a suit contract (distributional hand). If you have flat distribution (also called balanced distribution), then decide how high you think the partnership should be. If the partnership has fewer points than 26, PASS her 2NT bid. If the partnership has 26 or more points, then bid 3NT.
If you have a long suit or a singleton in a suit that your partner has not bid, then your hand will probably play better in a suit contract. Since your partner has bid NoTrump, she has to have at least two cards in all of the suits (her hand has flat distribution). Therefore, sometimes you can discover that the partnership has a fit in the other major suit and can add support points to your hand! Of course, for you to know that the partnership has a fit in the other major suit, you'll have to have at least six of the major suit yourself. [Six in your hand, plus two in her hand add up to the eight that the partnership needs for a major suit fit.] You also know that she has 17 to 18 points (or an excellent 16 points) so you can determine the partnership's total points. If game cannot be reached, you can bid 3 of the major suit saying "we have lots of this suit and not enough points for game." If the partnership has enough points for game, just jump to game in the major.
Rarely will you want to jump to game in a minor suit. Your partner has 17 to 18 points and you have 6 to 9. I'm sure that you remember that a minor suit game generally requires 28 points in the partnership's hands. So the number of points will very rarely add up to game in a minor suit.
So, if you have a long minor suit, you have to make a decision: will your hand play better in a suit contract or do you think she will be able use your long minor suit to "run" tricks at NoTrump? Don't forget that she has at least two cards in the suit and is going to hold some kind of stopper in the suit. Suppose you hold:
♠8 ♥987 ♦AQJT73 ♣642
Your partner opens opens 1♠ and you respond 1NT. Then she bids 2NT. You can be certain that your partner has the ♦K for her stopper in diamonds. So the partnership is very likely to have six tricks in diamonds without counting any tricks in the other suits. She also has 14 or 15 points in the other suits which is very likely to take three tricks. So just bid 3NT. You have 9 points and she has 17 to 18, so the partnership has the necessary 26 (or 27) points for game. You also know that your hand will provide lots of tricks for the partnership because the opponents will not be able to take a trick in the suit. [They don't have a stopper.]
If you have a long minor suit which will not run (or you're not very sure), you can still bid NoTrump but you have to be certain of two things: a) that your suit will be ready to run after the opponents take their one trick in the suit (their stopper); and b) that your partner can get back to your hand to use the length cards you have there (you have an "outside entry" to your hand). [The opponent's suit has to be stopped twice too, but this is much harder to determine.] You hold:
♠753 ♥9 ♦KJ8743 ♣Q73
After she opens 1♠, you respond 1NT and then she rebids 2NT. It's very likely that the opponents have at least one stopper in diamonds. Once the opponent's stopper is gone, your partner will have to get the lead into your hand in another suit (most likely). Your ♣Q is not certain to take a trick so you don't have an outside entry to your hand. So this one's not going to work in NoTrump very well. Your hand isn't likely to take many tricks unless diamonds are trumps. Since you have a nine loser hand and your partner has a six loser hand, you should just bid 3♦. If you have
♠753 ♥9 ♦KT9632 ♣A63
you should probably bid 3♦ too. Here, however, you do have an outside entry. The problem here is that your diamond suit is pretty ragged and your partner is probably going to need more than just one honor to ensure the partnership can take even five tricks in the diamond suit alone. A hand which probably qualifies for a 3NT bid would be something like:
♠753 ♥9 ♦QJT932 ♣A32.
Your partner's honor will help "set up" the suit. After the opponents take their diamond stopper, your partner can now use clubs to get to your hand and to keep playing those diamonds.
If you have a very long minor suit which will probably not be useful at NoTrump and your hand is sufficiently strong (mainly count losers for this kind of bidding), you can jump directly to game. [But always try to think of NoTrump before thinking of a minor suit game. The level of the contract is two tricks lower and is thus sometimes safer.] If you have:
♠72 ♥83 ♦void ♣KJT876532
Your partner opens 1♠ or 1♥, you respond 1NT and then she rebids 2NT. You can go directly to game and bid 5♣. You have six losers and your partner has six losers (strong opening hand) which indicates 11 or 12 winners for the partnership. Yes, it's possible that the opponents can set 5♣ and it's possible that your partnership might have a slam in clubs. There's just no way to find out whether your partner has all of the necessary ingredients to make slam or even to allow game to be made. This is a situation where you're having to make a guess but you're not guessing completely in the dark. Your partner has shown stoppers in spades, hearts, and clubs. Your club suit is terribly strong. [If your partner has ♣Ax (where x is some non-honor card), then the opponents are very unlikely to take any club tricks since they only have two of them and you have the top two clubs.] You're hoping that your partner's spade stopper and heart stopper are accompanied by another trick somewhere. Since your partner has 17 to 18 points, she's going to have high cards somewhere in her hand and these high cards are very likely to take tricks. [The "worst" club holding she might have is ♣Q94 which means that your opponents only have the ♣A. But if she only has that in clubs (a questionable stopper in clubs, by the way) then she has 15 or 16 points in the other suits: likely to be aces and kings.]
If she bids 3NT, you just need to decide if you can live with this contract for the partnership. The thinking is similar to what I've been discussing when she rebids 2NT, but you now know that she has 19 to 21 points with five or so losers. You can PASS if you think that NoTrump is as good a contract as any, you can bid 4 of a long minor suit if you think that your hand is just too pitiful to get to game and you have a long ragged minor suit, and you can bid game in a minor suit if you're very uncertain about a NoTrump game. The latter choice is going to be a rare one but if you think that it's going to be best, go ahead and bid it. Sometimes PASSing 3NT and hoping for the best is a good idea since your partner is bound to have lots of stoppers.
Opener has reversed or jump shifted
In both cases, remember that she has told you that she has a strong hand (17 to 21 points for a hand which has reversed and 19 to 21 points for hand which has jump shifted). She has also told you about at least nine of the cards in her hand already: five (or more) are in the major suit she opened and four are in the second suit. [The times she will jump shift with only three cards in her second suit are very rare, so it pays to treat the second suit as a full four or more card suit until you start getting other information which might lead you to think otherwise.] That means that she has only four cards in the other suits. If you do not have a fit for your partner's suits and you have a long suit of your own, you must beware of a misfit: she could have a void in your suit! Thus, if you bid your own suit, you're indicating that it's a good suit. [It won't be a terrific suit since you have only 6 to 9 points. But something like KQT964 is a good suit. In a pinch, even something like QJT8763 might be considered somewhat good if you really have no fit with your partner's suit at all.]
When she reverses, you must make another bid even if you have a 6 point hand. The choices for your bids can be bidding 2NT with flat distribution and no support for either of partner's suits, showing some support for her first suit (rarely will you have true support since you didn't show the fit with your first response), supporting her second suit with four cards in the suit, or bidding your own suit if it's a good suit. You need to be aware that the last two choices tend to show hands with the top of the 1NT response range (8 or 9 points), so with very minimum minimum responding hands (6 or a bad 7 points) you might consider 2NT or 3 of her opening major suit.
When she jump shifts into another suit, you also have to bid again, but 2NT is not going to be an option for you (all jump shifts will be at the 3-level). Just as when she has reversed, you can support her first suit (rarely with true support), support her second suit with four cards in the suit, bid your own suit if it's a good suit, or bid 3NT. However, when bidding 3NT you should try to have something resembling a stopper in the unbid suits. [It probably doesn't have to be a full stopper since she has so many points. Something like the Qxx or Jxxx would probably be enough in this case.]