Here are guidelines for opening, responding and rebidding if your system uses old-fashioned Strong Two-bids. Note that many pairs now use the more popular Weak Two-bids where 2D, 2H and 2S show hands with 5-10 pts. and a good 6-card suit. If you play Weak Two-bids, an opening of 2C is an artificial bid showing a strong two in an unnamed suit.
An unbalanced hand of 21+ points. You may open with fewer points if your suit is long and strong and your hand meets the other requirements.
A good, 5+-card suit (preferably a 6-card suit, especially if it's a minor).
Good quick tricks and controls in the other suits (aces, kings or shortness).
Playing strength to take at least 8 1/2 to 9 tricks if your suit is a major; 9 1/2 to 10 tricks if your suit is a minor.
Open 2NT with 20-22 points. (If you play an opening 1NT is 16-18, use 21-23 for your 2NT opening.)
Open 3NT with 25+ points.
With 0-6 pts. and no aces or kings -- bid 2NT. This is an artificial negative bid.
With 7+ pts. and a good suit of your own (a 5-card or longer suit with good honor strength) -- bid your suit at the cheapest level possible.
With 8-10 points and a balanced hand -- bid 3NT.
With 0-4 pts. and no aces or kings -- bid 2NT.
With 5+ pts. or any hand with an ace or king -- raise partner's suit.
Rebid your suit if it is 6 cards or longer.
Bid your second suit (4-cards or longer).
Raise partner's suit response (if you have 3+-card support).
Bid notrump to deny a fit for partner's suit and show stoppers in the unbid suits.
If partner shows a very weak hand by responding the negative 2NT, be careful. If you aren't certain of making a game in your own hand, keep the bidding low to give partner a chance to pass if he has absolutely no help for you.