Order is easier to keep than to recover. Most of keeping order happens before the room is noisy.
If you call for order in an annoyed voice, the house becomes annoyed. If you call for order calmly, the house becomes calm.
Never yell. A chair who shouts has told the room that shouting is how you get attention here.
Call the house to order. Then stop talking.
Do not carry on immediately. Stay silent and look at the room. The talking stops on its own, usually within a few seconds. The silence you get that way lasts far longer than the silence you get by talking over people.
Carrying on immediately after calling for order is one of the most common chairing mistakes. It teaches the room that the call for order was not serious.
The small rules are what hold the big ones up.
Placards stay down until the chair asks for them.
Delegates address the chair and the house before their speech.
Delegates speak in the third person.
A delegate yields the floor when the chair tells them to.
Eating and drinking during debate is not in order. Water is the exception.
No delegate leaves the room during debate without permission.
See Parliamentary language and decorum.
Letting delegates leave during debate without permission is how a committee empties. Once three people have gone to the corridor without asking, everyone goes.
Formality is not decoration. A room in which everyone says "the honourable delegate of Brazil" cannot easily descend into an argument, because the language does not allow it.
When a debate is getting heated, tighten the formality rather than raising your voice.
Nobody insults any member of the house, any guest, any member of staff, or the secretariat.
When a delegate uses language that crosses the line, stop them, ask them to withdraw the remark or rephrase it, and move on.
A public apology is only required when a delegate has insulted another person directly. An insult aimed at a political position is not a personal insult. If you are not sure, do not take the apology. Ask the delegate to stop using unparliamentary language instead. Never stage an apology in front of the house. Handle it privately or in writing.
If you are unsure whether it was personal. Ask yourself whether it was about a country's policy or about the person holding the placard. Policy is fair. The person is not.
If the room has genuinely gone, take a short break rather than fighting it for twenty minutes.
Announce it as a time, not a length. Say "we will meet again at 12.30". Add five to ten minutes for people to settle.
In MEDIMUN, during a break the committee state in MediBook is waiting, and roll call is taken again when the house returns. See The chair's committee state and Roll call.
Some rooms need more than a chair. If a delegate refuses a direct instruction, or the disorder is about conduct rather than energy, that is no longer a chairing problem.
Deal with the individual rather than the room, and escalate. See Difficult delegates and Chair reporting a problem.
In MEDIMUN, a delegate who breaks the code of conduct cannot receive an award. Say that once, at the start, and do not use it as a threat afterwards. See The code of conduct and Awards eligibility.
Do not use sarcasm to bring a room back.
Do not single out one delegate for something half the room is doing.
Do not threaten anything you are not going to do.
Do not keep talking while the room is talking.