The IDD code for France is 33. To call a number in Paris from the U.S., the + in +33 requires you to dial "011-33" and then the rest of your number. From within France, Paris' eight-digit numbers must be preceded by 01, and the IDD code is not necessary. Thus from within France, +33-1-23-45-67-89 would be dialed "01-23-45-67-89." If you have a cell phone or need to call a cell phone number, most of them begin with 06.
Public transportation is the way to go in Paris. The M?tro is easy to use and cheap. If you are in Paris for at least a few days, buy a Carte Orange hebdomadaire (weekly pass), which will quickly pay for itself. If you plan on being in Paris less time or not taking the metro, buy a carnet of 10 tickets, about the price of seven one-way trips, at any subway station. They're good on buses, too, which is an incredible way to experience the sights and sounds of the city. Unless you are in Paris for fewer than two days, a carnet will quickly pay for itself. Also if you're brave, try the bus system; it's the cheapest moving tour of Paris' streets, with the 67 bus a particularly enjoyable route.
If you need to take a taxi, be warned that you may come across some of the most impolite and embittered people in the city. They may not stop for you, and it is impossible to know if they're cheating you or not. The best way to get them to help you is by saying s'il vous plait and merci. Of course you may have great taxi drivers there -- may we all be so blessed.
You can save time ordering tickets for the permanent collection at the Louvre by phone (+33-1-49-87-54-54) or at FNAC record and bookstores. For additional trip-planning information contact the French Government Tourism Office (France-on-Call Hotline: 410-286-8310) or Paris Tourist Office.