Responder is the only one who can use New Minor Forcing and only after opener's second bid is 1NT (or, by agreement, 2NT). 

West	North Opener	East	South Responder
	1	Pass	1
Pass	1NT	Pass	2*

*New Minor Forcing

You can learn more about this convention in Larry's Webinar. 

The opening bidder is the only one who can make a support double. The condition for it is after an opening bid and response, an intervening call is made (either a bid or double). For example:

West Opener	North Opponent	East Responder	South Opponent
1	Pass	1	1

This is an auction where West could make a support double. Support doubles can only be made below two of the responder's suit. If South had overcalled 2 on the auction above, there would be no support double. 

You can find out more in Michael's Webinar on many types of doubles. 

Any position can use Roman Keycard Blackwood. Whoever chooses to use RKCB must be committing to bid slam missing only one keycard. Use Keycard Blackwood when you are definitely going to slam unless missing a keycard (or a keycard + queen of trump). If you aren't sure you belong in slam, use control bidding. Do not use RKCB if you might lose the first two tricks in a suit. 

You can learn more about Keycard Blackwood in this webinar with Michael

Only the responder can use Jacoby 2NT and only with no interference. If there is an overcall of a suit, then 2NT becomes natural and invitational. If there is a double in between, then 2NT (with agreement) is a slightly different convention called Jordan. 

You can learn more about Jacoby 2NT in this webinar by Mike Lawrence.

Overcaller. A Michaels cue bid shows 5-5 in the majors or, if the opening was a major, then 5 cards in the other major and 5 in an unspecified minor. How strong a Michaels cue bid should be depends on vulnerability and seat. The overcaller here might also be in fourth position as in 1 - (P) - 1NT - (2). 

You can learn about all types of cuebids including Michaels in this webinar with Larry.

Cue bids can have many possible meanings--they are simply ways to force partner to bid again. That said, any position could use a cue bid to show support for a suit partner has bid although sometimes the cue bidder may need to clarify the meaning later on. 

You can learn about all types of cuebids including support showing cuebids in this webinar with Larry.

Responder is the only one to use fourth suit forcing. This convention only comes up in non-game-forcing auctions. If the auction begins with a game-forcing 2/1 bid (1 P 2) then this convention is off. Fourth suit forcing will arise when opener has bid two suits (and not reversed) 

West	North Opener	East	South Responder
	1	Pass	1
Pass	2	Pass	?

On this auction South could use 2 as Fourth Suit Forcing. 

You can learn more about 4th suit forcing in this webinar with Larry