As the TD at a recent Sectional told me "people are bidding 2
♣ on weaker and weaker hands these days". This after an opponent opened 2
♣ on S AKQJxxxx and out, and then jumped to 4
♠ over his partner's 2
♦ negative. Our teammates, expecting opener to have rather more than ten HCP misdefended, and allowed 4
♠ to make. We got snookered.
Paul Soloway suggested that a 2
♣ opener ought to have more quick tricks than losers. That seems to work, provided you play that if opener bids and rebids his suit after a negative (or "double negative") response, responder can pass.
There are basically four ways to play responses to 2
♣:
1. 2
♦ negative (usually 0-7 HCP). Often coupled with "cheaper minor second negative" to allow bailout below game. This is IMO the worst of the bunch.
2. 2
♥ "double negative" (0-4 HCP or so). 2
♦ is then GF, with at least a couple of queens, but no good suit. With a good suit, you show it. 2NT shows hearts.
3. "Step responses" showing HCP. 2
♦=0-3, 2
♥=4-6, etc. I was wrong.
This is the worst of the bunch.
4. Control showing responses. There are several possibilities here. I like 2
♦=0 or 1, 2
♥=2, 2
♠=3, 2NT=4, 3
♣=5,3
♦/=transfers, showing a weak 2 in
♥/
♠ respectively. This works particularly well when 2
♣ is absolutely FG unless opener rebids 2NT showing 23-24 HCP.
I like Romex, which has some interesting agreements in this area. First, when looking at strong balanced hands, the number of controls is key; HCP are secondary. Second, when looking at strong unbalanced hands, LTC and controls are key - such a hand must have no more than 3 losers, and at least 6 controls. Third, Romex has
four strong opening bids, not just the two of SA or 2/1.
The biggest problem with having only 2
♣ and 2NT as the strong opening bids is that there are hands too strong for an opening one bid and too weak for 2
♣. You end up either stretching your one bids too far up, or reducing your 2
♣ bids too far down. Romex fixes that problem by opening those hands with one of its four forcing openings.
If I can't play Romex, I'd go with Soloway's rule, and either option 2 or option 4 above. I should probably add that I've read somewhere that Benito Garrozo, who kind of invented control showing responses back in the 1950s, now believes that it's more important to show shape than controls. <shrug>