You open 1NT. What is your rebid over partner's response of 2♣ (Stayman), 2♦ (Jacoby-transfer), 2♥ (Jacoby-transfer), 2♠ (weak, long minor suit), 2NT (natural), 3♣ or 3♦ (both natural, slam invitational or stronger) respectively?

Solution

Over partner's 2♣ bid (Stayman) you bid 2♠, showing your four card suit. At the same time you deny possession of a four card suit in hearts.

Over partner's 2♦ bid (Jacoby-transfer) you do what you have to do: you bid 2♥.

Partner's 2♥ bid (Jacoby-transfer) makes you very happy. He shows five spades or more. In view of your super fit (nine cards at least) and maximum hand you have ample reason to 'break' the transfer: you bid 3♠. This enables partner to bid game on rather modest values. If you content yourself with an 'obedient' 2♠ bid, partner doesn't know about the fit. Holding, for instance, 7 good points or 8 points he will pass 2♠, not wanting to risk going down. With your actual hand you will probably miss game then.

Over partner's 2♠ bid you rebid 3♣. Partner's conventional 2♠ bid (quite common in Europe) shows a weak hand and a long minor suit. He wishes to play either 3♣ or 3♦ ('contract improvement', compared to 1NT). Holding clubs he will pass your 3♣ bid, holding diamonds he will correct to 3♦, after which you pass.
Aside: this is the simplest way of playing transfer bids for the minors.
There are many more methods. Many pairs nowadays play 2♠ as a transfer to clubs and 2NT (watch it: danger of forgetting this!) as a transfer to diamonds. In this method the transfer bidder can have a stronger hand: invitational for game, game forcing or slam invitational, anything goes. The 1NT opener shows a fit (Axx, Kxx or Qxx or better) at once by the cheapest possible rebid (2NT or 3♣ respectively), in other words by 'breaking' the transfer. Obeying the transfer (3♣ or 3♦ respectively) denies a fit.

Over partner's 2NT bid (natural, so we assume NS not to play the transfer bids as explained in Aside) you bid 3NT. Partner requests you to bid 3NT holding a maximum hand and pass holding a minimum hand. You hold an absolute maximum!

Partner's 3♣ or 3♦ bid (slam invitational or stronger) improves your hand (and it was a good hand already). You definitely want to be in a slam. How to show that is a matter of agreement.
A simple way to accept the slam invitation is to raise partner's suit by bidding 4♣/♦ respectively. You voluntarily pass 3NT, conveying a crystal clear message.
Since such a raise will cost you a bidding level, many pairs choose a different approach. The idea is that the 1NT opener bids 3NT (a sign-off) if he is not interested in a slam. Any other bid shows willingness to play a slam, establishes partner's minor suit as trumps and is control showing. If you bid along these lines your rebid is:
- 3♦ over partner's 3♣ bid: 'Slam sounds fine to me, clubs are trumps, diamond control.
- 3♠ over partner's 3♦ bid: 'Slam sounds fine to me, diamonds are trumps, spade control, no heart control. If partner lacks a heart control as well, North now signs off in 3NT.