Opening 1C indicates 16 or more points. It is a demand bid for at least 1 round. A response of 1D is the weak response that shows 7 or fewer points while saying nothing about any suits, while all other responses show 8 or more points and are forcing the bidding to continue until game level is reached.
Responses to 1C Open for Beginning Precision
Responding with anything other than 1D indicates that you have 8 or more HCP and is thus game forcing!
Bid a 5 card major; 1NT with a balanced hand and no 4 card major; bid 2C with a 4-card major (Stayman); or bid your strongest minor at the 2 level if nothing else applies.
We will get to transfers and other things later but let's keep it simple for now.
After your first response all bids are natural. Gerber and Roman Key Card systems are on.
When opener gets the 1D response indicating less than 8 points, he should bid a 5 card major. Lacking that but with a balanced hand, bid 1N with 16-19 HCP, 2N with 20-23, and 3N with 24-27, etc. going up by 4 points for each level. Later on, we'll see how using a heart relay makes this all the more precise but let's keep it simple for now. Although the responder has already indicated having fewer than 8 points, with sufficient points, Stayman and transfer systems are on when opener bids No Trump.
Intermediate Precision Responses - Forward
As the submissive hand, responses should tell the opener as much as where you do not want to be as well as what is in your hand. Use Jacoby style transfers to avoid preempting the opening partner: 1H indicates a 5+ spade suit, 1S indicates a preference for NT, having no 4 or 5 card majors. 1NT says you have an unbalanced hand with a void or singleton in some suite, while 2NT says you are at least 5-4 in the minors. Responding 2C is similar to Stayman but is also the catch-all when nothing else applies. 2D indicates 5 hearts. 2H and 2S shows 6+ cards in the suit (no need to transfer).
The opener is under no obligation to accept a transfer. In fact, when a transfer to a suit is accepted immediately, it should be treated as a slam investigation in the first of a series of special asking bids. For more on slam bidding, see
Searching For Slam . Bidding anything but the transfer suit does not necessarily reject the suit, but since we are already forced to bid until we reach game level, either of us can come back to it when appropriate.
Note that the bidding sequence of 1C (2C) 2D is similar to the sequence of 1D (2D) or 2C (2D). It suggests that opener does not have a four card major and is probably more interested in no-trump possibilities. However, lower your response ranges from 11 and 14 down to 8 and 11. That is, respond at the 2 level to show 8 to 10 points and at the 3 level to show 11+ points. Responding with 2NT shows exactly 8 HCP and does not say you have stoppers in both majors.
Either side can jump to Gerber with 4C.
Intermediate Responses to 1 club open
1D, less than 8 points (says nothing about shape)
1H, 8 or more HCP, 5 spades (opener announces "transfer to spades")
1S, 8 or more HCP, balanced hand with no 4 card major (opener alerts and if asked says "8+ points and balanced hand (interest in playing in no-trump)"
1N, 8 or more HCP, a very unbalanced hand (usually containing a void or singleton somewhere, prefering not to play in no-trump)
2C, 8 or more HCP, similar to Stayman, usually shows having at least one 4 card major
2D, 8 or more HCP and 5 or more hearts (opener announces "transfer to hearts")
2N, 8 or more HCP and 5-5 or better in the minors
Responding to a 1C open after interference
Well, aren't you lucky! You now get 2 extra bids to consider: pass and double (if the interference is a double, then you have a redouble option). If you have 0 to 4 points, pass (opener still has another chance to bid). With 5-7 points and a 5 card suit, transfer as outlined above. With more than 7 points, or to indicate a stolen bid, double. Opener may or may not accept your transfer. With more than 7 points, help push the bidding up to to the 3 level in no-trump or otherwise the 4 level by doubling or bidding the next level of clubs (you will be forgiven if it is not meant to be a transfer to diamonds). Avoid bidding new suit majors unless you have less than 3 of them so you don't get stuck as declarer
Consider the following deal:
s 965 s t84
h A7632 h t8
d 74 d AK9632
c 752 c A8
North opens 1 club and East overcalls 2 diamonds. South doubles to show 5 to 9 HCP and West bids 2 hearts. North doubles this to show 4 spades, East passes, and South, having 4 good hearts and short in spades, is ready to leave the double in place. East returns to 3 diamonds, which North again doubles but this time for penalty considering the point counts. EW is stuck with nowhere to go, end up going down 2 (doubled) giving NS a score of 300.
While NS could not have made game in any suit or in no-trump, they get enough information from East's interference to settle for a better set score, where they otherwise might have stopped at 3 or 4 in clubs, or possibly in no-trump but getting set.
More fine details on responding to a 1C open
Distribution ranges for 1S, 1N, and 2C responses to 1C open
1S from 13xx - 23xx
1N from 34xx - 43xx not including 3424-3442 and 4324 - 4342
2C from 3424 - 3442, 4324 - 4342, and 13xx - 33xx
After 1C (2C) 2H, responder now has 3 choices: 2N means 3 or fewer hearts, 3C means 4 hearts, and 3H means 5 hearts. Opener can then bid a side suit to show 5 hearts and 4 of the side suit, or bid 4C for Gerber, or 3N. Even with a 5-3 heart suit fit 3NT is best with square hands.
A Precision conversation translated into English
(Opener) 1 club: Hey, partner. Good news! I have an strong hand - at least 16 high card points. I'm not going to describe my distribution yet so we can keep it secret from our opponents, but tell me what you've got.
(Responder) 1 diamond: Sorry, partner. I can't commit to game level until I get more direction from you because I have less than 8 high card points.
(Opener) 1 heart: Bummer, dude. But let's see if we can salvage something. Before I go on, do you have any of the special distributions that we have discussed?
(Responder) 1 spade: Nope, nothing special. Anything else you want to know?
(Opener) 1 no trump: OK, I have a pretty square hand with either 16 or 17 points. I still might have a 4 card major suit in case you're interested.
(Responder) 2 clubs: Yeah, I am interested because I am near the top of my high card range and either have a long minor suit or a 4 card major myself, so we should take a look at that.
(Opener) 2 diamonds: I took a closer look -- don't have any 4 card majors. Should we just leave it in diamonds or go back to no-trump?
(Responder) 2 hearts: I have either 4 cards or at least a stopper in hearts but I'm a little concerned about no-trump since I have next to nothing in spades.
(Opener) 2 spades: Now you have me worried about no-trump as well because I don't have a stopper in spades either. You'd better transfer me to your best minor suit.
(Responder) 2 no-trump: My best minor suit is clubs.
(Opener) 3 clubs: Whew, we just dodged a bullet. We would have maybe lost 5 tricks in spades and 1 each in the other side suits, getting set in 1 no-trump. We're pretty safe in 3 clubs with our fit and my 16+ and your 5+ points.
(Responder) Pass: Great. Let's see what they throw at us.