As a somewhat newish player, I'm hesitant to stray far from the precepts of the cheat sheet I learned from. But we have made a few deviations, largely according to the wisdom of Bryan, and I'd like to enumerate those for everybody, in part to avoid fouled-up Stayman contracts like the one I played last night.
The cheat sheet says, for example, that you can respond to 1NT holding a five-card minor suit with 6 points, which is what screwed us up last night. That's great but incorporating four-suit transfers into Stayman seems to work better. If I may loosely quote myself, for the record:
To respond to a 1NT opening, you should have 8+ points. A response of 2D shows five hearts, 2H shows five spades, 2S shows five clubs and no four-card major, and 2NT shows five diamonds. To show a balanced hand, bid 2C and then rebid 2NT when it's your turn again. (Any of these bids can be made at the 3-level instead, which promises maybe 12 points and is forcing to game.) A 2C response is Stayman, showing at least one four-card major suit. Responses by opener to 2C are: 2D in the absence of a four-card major; 2H with four hearts (may also have four spades); 2S with four spades (implies fewer than four hearts). Memorize this.
The cheat sheet says you can overcall with 8 points; if you have opening strength, make a jump overcall. That's great but its primary usefulness seems to be gumming up the opponents; it doesn't give partner, who'll have his own chance to bid anyway, very much information. We've started requiring 13 points for an overcall. I'm happy to hear opposing views on this though.
3. MEDIUM TWOS
The cheat sheet says if you have 18-21 points, you must bid one of a suit and then jump shift. An opening bid of two of a suit promises game in your own hand. That's great but as I have complained before, I often get passed before I can jump. That's why we've been saying that you can bid two of a suit with 18-22 points, which is forcing for one round. Nobody's ever been dealt game-in-hand in my experience, not even Twenty-Point Jeff, so I'm not terribly worried about how to deal with that situation.
If you play with us and you see that I'm leaving something important off the list, please let me know. If you don't play with us and one of the things I'm proposing seems wrongheaded, please please let me know, gently.