Usage patterns
マナーを学ぶto learn manners/etiquette
I learned the local etiquette before traveling abroad.
マナーに欠けるto lack manners
That customer's attitude was lacking in manners.
〈場所〉でのマナーetiquette in a place/setting
Let's follow proper etiquette in the library.
マナーモードにするto switch a phone to silent mode
Please switch your phone to silent mode in the movie theater.
Expressions
マナーを守るmind one's manners; follow the rules; be civil