In France, "Bonjour" before anything else isn't a politeness tip — it's the gate. Without it, the cashier may not serve you. The bus driver won't acknowledge you. Get this wrong and you become "the rude tourist."
The "bonjour" rule isn't about politeness — it's about acknowledging the other person's existence before imposing on them. In France, walking into a shop and saying "Je voudrais..." without first saying "Bonjour" is genuinely rude and the person behind the counter may refuse to help you.
The other rule: "Bonjour" is only until ~18h, then "Bonsoir." After ~22h, "Bonne nuit" is OK but rarely used. Morning "Bonjour" returns the next day. Get the time wrong and you sound either old-fashioned or touristy.
The right word for your time, context, and relationship — including regional twists (Toulouse uses "Bon" alone).
Once you've bonjour-ed, the natural next sentence — including "S'il vous plaît" placement and how to ask the actual question.
How to close the exchange — "Merci, bonne journée," "Au revoir," or "Bonne soirée." Yes, both. Yes, in that order.
It happens. The server will often correct you with a polite "Bonjour" prompt. Say "Bonjour, pardon" (Bonjour, sorry) and continue. Don't make a scene.
From about 17h–18h onward. After sunset is even safer. In summer (when the sun sets at 22h), you can still say "Bonjour" until ~20h. Follow local cues.
No, not in service contexts. "Salut" = "Hi" among friends/peers. Use only with people you've already greeted as equals.