With a balanced hand, opener will be rebidding no trumps according to their original plan, so it is not a difficult decision what to choose.
With an unbalanced hand, inexperienced players tend to worry a lot about their partner passing a simple rebid and so make a jump bid on an inappropriate hand. In the rare occasion that partner passes your simple rebid, it is unlikely that you could ever make a game contract and possible that your opponents will bid and allow you to show your strength.
A jump rebid, in a new suit below your original suit, is GAME FORCING. This means that neither partner can pass until game is reached. Opener must have a strong hand to make a jump rebid, since you are forcing to game opposite a possible six points.
Examples:
S xx H AQJxx D x C AKQJx Open 1H, your highest 5-card suit and you plan to rebid 3C over a 1S or 1NT response. This is a minimum hand for a jump rebid. | S xx H AQJxx Open 1H and rebid 2C over 1S or 1NT. You are not strong enough to game force but you may bid again to show you are close. |
S Kxx Open 1H and rebid 3C over a 1S response and 2C over a 1NT response. Your hand improves to a game force when partner shows a spade suit. | S AKxxx Open 1S and rebid 2C over a 1NT response. You can continue with 3C over partner’s next bid to show a good, distributional hand without the values for a jump rebid. |
S Kx Open 1H and rebid 2H over 1S or 1NT, showing a minimum opener with six hearts. | S xx Open 1H and rebid 3H over a 1S or 1NT response. This is an invitational bid to game. |
There are two other strong rebids available to opener: a jump shift to the two-level and a reverse.
S xxx H AQJx D x C AKQJx Open 1C and rebid 2H if partner responds with 1D. This jump rebid is forcing for one round only. | S xxx H AQJx D x C AKQJx Open 1C and rebid 2H if partner responds with 1S. This is known as a reverse and it shows a strong hand, typically 16+, and shows that the second suit is shorter than the first suit. This rebid is forcing for one round only. |
If you have four-card support for partner, then you should raise. A simple raise shows a minimum opener. A jump raise shows better than minimum and is invitational. A jump to game shows a maximum one-level opener.
If you have three-card support for partner and an unbalanced minimum hand, then it is often a good idea to raise partner immediately. The ability to ruff makes up for the lack of a fourth trump.
If partner makes a weak jump shift at the two-level, then they have defined their hand fairly accurately.
Opener can make a forcing 2NT bid to ASK further about responder’s hand. Responses as per a weak two-level opening bid.
Opener’s rebid of his original suit is non-forcing and to play.
Opener’s new suit is forcing for one round.