French is the most widely spoken language throughout Paris and the only official language there, but since it is an international destination, you may find people speak English, German, and Italian, as well as other languages.
Memorize key French phrases such as "parlez-vous l’anglais" (do you speak English?) and "merci" (thank you) before you go. Duo Lingo is a great app for learning basic French in a fun and fast way. You can also write phrases on a note card or in the Notes app of your phone for a handy cheat sheet during your travels.
In addition to greeting others with "Bonjour" (Hello), it is preferred to formally say "madame" to women and "monsieur" to men.
To order in a restaurant, use the phrase "Je voudrais" (I would like) followed by what you’d like to order. For instance, "un verre de vin" (a glass of wine) or "pain grille" (toast). Also use the phrase "s'il vous plait" (please).
On leaving restaurants and shops, take a moment to say, “Merci, au revoir!” This is considered proper and if you don't it's considered bad manners.
Other helpful phrases include "Où se trouve" (Where is) and "Combine coûte" (How much is) when navigating about Paris.