[Kaitlyn S]

Stayman is used to find a 4-4 fit without the responder having to bid (or transfer to) four-card suits in auctions where it is valuable to have the responder be able to show a five-card major. Transfers are used to make the stronger hand the declarer.

1D-(p)-1N-(p)-
Opener wouldn't use Stayman to ask for responder to show a four-card major that responder has already denied.
2C is natural, showing four or more clubs and at least four diamonds.
There is no reason to transfer even if opener has a five-card major (and six or more diamonds) because opener can bid the suit naturally.

1H-(p)-1N-(p)- Again, opener has shown five hearts already, and most responders have denied four spades so neither convention is necessary.

1D-(p)-2N-(p)- I play that 2NT denies a four-card major so no reason for Stayman (and not for transfers either.) Even if responder could have a four-card major by agreement, I think it's better to have the opener (the less described hand) declare to keep opener's shortness (if any) in the dark from defenders.

1S-(p)-2N*-(p)- *Assuming a natural 2NT, not jacoby 2NT.
Here responder can have four hearts but opener can show four hearts by bidding them.

2N-(p)- It is normal to play Stayman and transfers here.

2C-(p)-2D-(p)-2N-(p)- This is just like a notrump opening so Stayman and transfers are normal here.

2C-(p)-2H-(p)-2N-(p)- Since responder is already declaring a heart contract, there is no reason to transfer. Also, since responder can just bid 3S to show spades, it's more valuable for responder to be able to use 3C to show clubs.

1D-(p)-1S-(p)-2N-(p)- Again, responder is playing a spade contract so there is no reason to transfer. Some pairs play "Checkback Stayman" or "New Minor Forcing" to look for a 5-3 spade fit or a 4-4 heart fit. In the absence of such an agreement, I would assume that 3C is natural and forcing (there is some merit to having it be a weak hand with 4 spades and 6+ clubs by agreement.) The responder can bid 3H to show hearts. Many pairs that do play Checkback Stayman or New Minor Forcing say that 3H here is non-forcing (choosing to bid the convention with game-going hands.)

[dokoko]

simple rule

Stayman and Jacoby is on, if

a) we open 1nt or 2nt or some equivalent [like 2c(str art)-2d(waiting)-2nt or 1c(str)-1d(wk)-1nt or the like] or
b) we overcall 1nt or 2nt (natural) in direct or reopening position

and opponents pass over the nt bid.

Stayman and Jacoby is off, if

1) opponents bid over the nt bid (including dbl) or
2) nt is bid by responder (to opening or overcall) or
3) we bid a suit naturally before the nt bid.

You may use these conventions in some #1 or #2 situations, but these are non-standard and require explicit discussion.
You may use a convention named Checkback (which is a Stayman variation taking into account the previous bidding) in some #3 situations where opener's nt is preceded by natural bids. This is advanced stuff and requires discussion as well.

Edit:
reasons for a) and b) are that the basic situation is similar to responding to a nt opening. If opponents already bid naturally you might not see reason to play in their suit but you can if you want to.

reasons for 1) are that in case of a dbl your objectives have changed (less need for constructive bidding, more need for weak take-outs to a suit) and in case of a non-dbl your bidding space is reduced.

reasons for 2) are that you might prefer the strong hand not to be dummy and also the strong hand might want to bid a minor naturally.

reasons for 3) are that the conventions would ignore the info already given which is kind of waste.

[helene_t]

Btw, even if
2♣-2NT
3♣*
may be Stayman (debatable),

2♣-2NT
3♦*
is certainly natural.

[Vampyr]

Stephen Tu, on 2017-August-03, 10:42, said:

I first saw this suggested in Root/Pavlicek's Modern Bridge Conventions published 35+ years ago, which was my first book on conventions (I still think it's the best first book, way more thorough in covering responses than most others) , which is probably why I don't find it odd.

It's possible that this book is the only place where this treatment appears, because I, like others had not heard of it before.

In any case, I find little need for a natural 2NT bid by responder. It is only getting in opener's way.

[P_Marlowe]

Hi,

Stayman / Jacoby Transfer are part of a NT response system, i.e. they apply, if the first natural bid
of the partnership was a NT bid.
Natural bids include short 1C / 1D openings.

If the auction is contested, after we opened with a natural 1NT bid, it gets messy, if they still apply.

They can also be used, after a NT overcall from our side, after the opponents oppened the bidding with a suit bid.

#1 (1S) - 1 NT - (Pass) - 2C
#2 (2S) - 2 NT - (Pass) - 3C
#3 (3S) - 3 NT - (Pass) - 4C

#3 is less common, but not out of space.

With kind regards
Marlowe

[P_Marlowe]

helene_t, on 2017-August-03, 20:11, said:

Btw, even if
2♣-2NT
3♣*
may be Stayman (debatable),

2♣-2NT
3♦*
is certainly natural.

I should this have added to my list as exception, no rule without exceptions,
..., and maybe no exception, without an exception.