Formal:
* Faites silence! (Make silence!) - This is the most formal way to say it, used in situations like a library or a classroom.
* Chuchoter, s'il vous plaît. (Whisper, please.) - This is a polite way to ask someone to be quieter.
Informal:
* Taisez-vous! (Shut up!) - This is a more direct and forceful way to say it, and is often used when someone is being loud or disruptive.
* Fais silence! (Be quiet!) - This is a more casual way to say it, often used with children or friends.
* Chut! (Shhh!) - This is a short and simple way to tell someone to be quiet.
Other options:
* Silence, on vous prie. (Silence, please.) - This is a more formal way to say it, often used in public announcements.
* Parlez moins fort, s'il vous plaît. (Speak more quietly, please.) - This is a polite way to ask someone to be quieter.
The best way to say "be quiet" in French depends on the situation and your relationship with the person you are speaking to.