Like, do you use tu or vous in this situation for your wording? Does it matter if you are trying to be more respectful or formal if you see a girl and are using lines to get a date with her?
In the case you describe, "tu" would be far more common. Bar/cafe are places you're in to relax. Most of the time, even waiters will use "tu" even if they don't know you.
"Vous" is formal and would not be used by most of the people, unless they want to seem lordy. An exception might be older people who might prefer to be "vouvoyées", even by people of their age.
People very lordy and/or old can even call each other "vous" even if they are married, like former French president Jacques Chirac and his wife Bernadette do.