Bridge & other card games/Responder's rebid
1C - P -1S- P-1Nt(12-14) -P - 2D
I am sure I was taught that responder's rebid after opener's rebid of 1nt is limited, showing 6-9 points but others disagree! Please could you clarify?
Secondly, how does bein vulnerable affect an over all at the 1 and 2 levels. I was advised that over calling a minor at the two level should be almost an opening hand. Is it the same with a major?
Traditional Standard American bidding teaches that after opener's rebid of 1NT, responder's rebid of a new suit at the 2 level, below the rank of his first suit, is indeed limited showing 6-9 or 10. In the modern bidding style, however, while a rebid of 2H is still limited, a rebid of 2D is generally played as "new minor forcing". In the auction that you give, 2D is artificial in that it says nothing about your diamond holding. Instead it shows a hand of invitational values or better...at least 11 points...and asks opener to show, in order of priority, three card support for responder's major (spades), four cards in the other major (hearts) or bid 2NT with neither. This allows you to find a 5-3 spade fit or a 4-4 heart fit at a low level. The same principle applies over 1D-P-1S-P-1NT- 2C where 2C is "new minor forcing" and says nothing about clubs.
Of course, you and your partner can agree to continue playing the traditional style.
As far as overcalls are concerned, at the 1 level vulnerable you should have at least 9 points and a decent 5 card suit. Not vulnerable you can lower the requirement to about 7 points but the suit should still be decent as you are encouraging partner to lead your suit if he is on opening lead and if you have five to the jack it could prove embarrassing.
At the 2 level, vulnerable overcalls should be close to an opening bid with preferably a six card suit with 2 honors. However, a very good 5 card suit, holding 3 of the top 4 honors is acceptable, although conservative players wouldn't do it. Not vulnerable you can have 10 or more points but the suit should still be good.