LAWS OF BRIDGE
David Cree has flowcharts concerning the most common laws for use by Tournament Directors. Contents list here.
Bridge is one of the few games where most of the participants know very little about the rules of the game. Certainly some of them are a bit complicated but one item causes more antagonism that any other and players should learn the general principles to do with UNAUTHORISED INFORMATION.
You are allowed to take advantage of anything done by your opponents at your table, but you are obliged to ignore any unauthorised information gained from your partner's actions. This includes failure to alert.
This can be very difficult to put into practice but if your partner fails to alert and it is obvious they have forgotten the system, you must proceed on the basis that the bid was alerted and treat your partner's bids as if they are playing the system.
The other difficult feature of unauthorised information is hesitations. This can cause a great deal of antagonism at the table, but really there is no need for this to be a problem.
If, in the bidding, a player hesitates it is beholden on their partner to make the bid they would always make if their partner had not hesitated. Some people think you must pass after partner hesitates. Absolutely not, you might be depriving the opponents of a chance of doubling you for a good score. Just bid normally, including doubling the opponents. What happens is that the opponents get two bites at the cherry. If your bid gives them a good score, they say nothing. If it is bad for them they can call the Director and point out the hesitation. What the Director has to do is decide if your bid is what most people (of your ability) would have bid with your hand.
So, don't get upset if opponents hesitate and bid on, agree that there was a hesitation and if the score at the end looks bad for you, call the Director.
Another case of Unauthorised Information which can be easily avoided is asking for the meaning of alerted bids. DON'T ASK unless you have an interest in taking action. If say the opponents bid 1NT - 2C alerted and you ask about 2C then pass, your partner cannot lead a club, unless it is completely natural for them to do so (e.g. QJTxx). If you do hold good clubs and want to double for a lead, by all means ask then double when told it is Stayman, if your told it is say clubs and another then you can pass. Partner though cannot lead a club unless it is a natural lead.
However, because you shouldn't ask the meaning of bids during the auction, declarer must inform the opponents of the meaning of all bids before the opponent leads. Very few players do this and it is bad ethics. If some bid had a special meaning inform your opponents, remember they shouldn't be asking during the bidding. Also if a bid was misexplained then you should clarify this before your opponent leads. Your opponents could get an adjusted score if they were damaged by the wrong explanation.
Related to that is when your partner gives a wrong explanation or fails to alert and you are defending. YOU MUST SAY NOTHING until the end of the hand and then inform your opponents. Again an adjusted score might be awarded if it caused damage.
By the way if you make the wrong bid but partner correctly explains it, there is no damage to the opponents as long as you both bid according to what you think it means. E.g. partner opens 1S and you bid 4C which you think is Gerber, partner alerts and explains it is a splinter (which is what you play). Partner shows no interest and bids 4S. You must proceed as if that is 2 Keycards and bid accordingly. Likewise the other way round you bid 4C splinter, your partner explains it is keycard (the correct meaning) and bids 4S. You should pass as partner is showing no interest to your splinter. If you get a good score out of a mix up like this then opponents' have no redress.
Finally if you don't know the meaning of a bid, don't say "I'm taking it as..." you are giving unauthorised information. Just say you don't know. Also with an unfamiliar partner just say NO AGREEMENT. The opponents have the same information as you and can use their knowledge to decide the likely meaning, you do not have to give lessons, just say no agreement. E.g playing with someone for the first time and with all 4 bidding : 1H - 1S - 2C - P - 2S which you alert and are asked, just say no agreement. They can work it out just the same as you can, with a regular partner of course you should be able to give a proper explanation.