Things to know about Duplicate Bridge

A hand is limited to 10 minutes in most novice games. As you get more experienced you get less time to play the hand. Most open games you get around 7 minutes to play each hand. You do tend to play 2 or 3 boards at the same time so a 2 board round is about 15 minutes and a 3 board round is about 21-22. The director can call the round early if everyone is done.

Count your cards when you take them out of the slot. Everyone should do this. Just because 3 people have 13 cards does not mean the 4th person will. A card could be lying on the floor. If everyone has 13 cards you can commence the bidding. If not, call the director and explain the situation.

When you are done playing out the hand and are putting the cards back into the slot SHUFFLE them before you put them away. That way the next table won't know the order the cards were played in.

At any point in the bidding process you may turn to the PARTNER of the person who made a bid and ask what the bid means. The PARTNER should tell you what they know about the hand rather than what the bid is called.
(When explaining a bid just don’t say “That’s a Jacoby Transfer” – instead say “that forces me to bid 2 Hearts – they have at least a 5 card Heart suit.”)
It is perfectly acceptable to say “I have no idea what that bid means!” (if you truly don’t!) Another (perhaps less embarrassing) way to say this is “We have not yet discussed this auction.”

When you make your opening lead place it face DOWN at the table and say “Any questions, Partner?” They can now ask about the bidding. Once you place your card on the table you are not supposed to change it. If you want to ask about bidding do so BEFORE you make your lead.

Did your Partner not follow suit? To make sure that they didn't revoke (not follow suit when they do have a card in the suit) you can say "No [Insert Suit], Partner?" Dummy is allowed to ask Declarer. Note that ALL players have a responsibility to make sure that Dummy doesn't revoke!

Dummy is NOT supposed to help Declarer in any way. So no prompting as to what card you think Declarer should play from Dummy.

What Dummy CAN and SHOULD do is make sure Declarer plays their cards from the correct side. As Dummy, you should NOT prompt Declarer as to where they are playing from. However if it looks like Declarer is about to play a card from the wrong place (say they grab a card from their hand but they are supposed to play from Dummy) you now can say "You are in your Dummy, Partner." If Declarer starts to point to a card from Dummy but they really should be playing from their hand Dummy is allowed to say "In your hand, Partner." However IF the card has already been played (or called) Dummy is NOT allowed to now tell Declarer where they should have played from. That is up to the Opponents. Quietly play the card you were asked to play.

Whenever an irregularity occurs please feel free to CALL the DIRECTOR. The director is your friend and should know all the rules to duplicate bridge. Sometimes at the table the Opponents tell you that you must (or can't) do something. When in doubt CALL the DIRECTOR. Sometimes people don't know the rules. Sometimes they know part of the rule but not the full rule. The director can help.

You can change your BID. You cannot change your MIND. What does that mean?
Say I intend to open the bidding 1♠ but instead I pull the 1♥ card from the box. Ooops! Before I place the card on the table I can easily change it. Note that before you place your bidding card on the table you really should check to make sure that you are making the bid you want to make. But sometimes we don't always do the things we should. What happens?
So let's say I intend to bid 1♠ but instead I pull the 1♥ and I don't bother checking the bid until it has been place on the table in front of the Opponents and Partner. Now I notice! Oooops! No worries. I just say something like "Sorry, I meant to open 1♠. Let me change that." The Opponents might question that -- "The bid has been made!" they might say. No problem. Just say "Let's call the director and ask whether or not I'm allowed to do that." When the director comes to the table make sure that you say that you intended to open the bidding 1♠ -- you just pulled the wrong card out. There will not be an issue.
What happens if your LHO (Left Hand Opponent) has made a bid BEFORE you notice. Well that's okay too! You can STILL change your bid back! (But now your LHO also gets to change their bid.) If the Opponents try to tell you that they've already made a bid so you can't change yours just simply say "Let's call the director". In fact I would encourage you to do that right away rather than telling the Opponents this is what you want to do. That way everyone knows the rules have been obeyed.
Can you change your bid at any point in time? NO. Once PARTNER makes a bid you are stuck.
That is the "You can change your BID" statement. What about the "You cannot change your MIND" part? Say I have two five card majors and enough points to open the bidding. I decide to bid the ♥ first like I was taught. Up the Line and all that. So I open the bidding 1♥. Once I make my bid I remember my teacher saying with two five card suits bit the higher ranking suit first. So I really should have opened the bidding 1♠. Can I change my bid now? NO. You are not changing your bid -- you intended to open 1♥ and that's what you did. You want to change your MIND. You have now decided opening 1♠ is a better bid (it is) and now want to make the best bid. Too late. You are not allowed to change your mind.