Don't
Loudness
It is considered very rude to be loud in a crowded place, such as a subway car or restaurant. Keep in mind that, though you may be enjoying your holiday, most people around you in the métro or other places are probably going to or back from work and may be tired and thus will react very coolly to tourists babbling at the top of their lungs.
Dress code
Dress codes are fast disappearing all over the country but very few French people will wear white sneakers, baseball caps and flip-flops (except at the beach). Nobody will tell you anything, you will just be labeled as a tourist. Generally speaking, business casual dress code is sufficient in cities and in all but the most formal occasions. Usual courtesy apply when entering churches, and although you may not be asked to leave, it is better to avoid short pants and halter tops. Some restaurants will frown if you come in dressed for trekking but very few will insist upon a jacket and tie. At the same time you'll be surprised by the number of French twenty-somethings who show up at a grungy bar in jacket and tie, even if obviously from a thrift-shop.
Sensitive topics France is not exactly the same country that one sees portrayed on American television. Its people have a wide variety of opinions about many subjects. Unless you really follow French news closely, you should probably steer clear of discussing internal French politics, especially sensitive issues such as immigration - you probably don't know much about them and will come across as judgmental and uninformed. Reading French newspapers to get a feel for the wide spectrum of political opinions in France – from the revolutionary Communist left to the nationalistic right – would help. Anti-French feelings, especially popular amongst the British and Americans, can be fueled by the inadvertent reduction of France to Paris, that is, that all French people act like Parisians, when this is quite far from the truth. Many rural people say that France is a blessed country, the inference drawn that it is cursed by Paris (or the Government. This also included the Germans, but is rare since the 50s). Paris is a fairly unusual city by French standards and life there is, in some respects, closer to life in London or New York City than in the rest of France. A traveler's experiences with French culture in Paris should be treated as one would treat an experience in the traveler's own country's largest cities; that is, the locals are hurried and "have seen it all". No doubt an American would not consider a trip to New York City as a typical American experience. Reserve judgement until having traveled far afield of Paris.
Source: Wikitravel.
Tips
Passport and Visa
France is a member of the European Union and the Schengen Agreement. European visa policy will be covered in the article about the EU. In brief, a visa to any other signatory state of the Schengen Agreement is valid in France too. No visa is required for citizens of other EU member states, and those of some selected nations with whom the European Union or France have special treaties. Inquire at your travel agent or call the local consulate or embassy of France. Also, there are hardly any border controls between France and other Schengen Agreement nations, making travel less complicated. However, sometimes cars and buses are stopped at borders or at the first toll-booth after entering the country.
Money
France is part of the Eurozone, so as in many other European Union countries the currency used is the euro (symbol: €). Some foreign currencies such as the US dollar and the British Pound are occasionally accepted, especially in touristic areas and in higher-end places. Furthermore, the merchant may apply some unfavourable rate. In general, shops will refuse transactions in foreign currency. Almost all stores, restaurants and hotels take the CB French debit card, and its foreign affiliations, Visa and Mastercard. American Express tends to be accepted only in high-end shops. Check with your bank for applicable fees (typically, banks apply the wholesale inter-bank exchange rate, which is the best available, but may slap a proportional and/or a fixed fee). There is (virtually) no way to get a cash advance from a credit card without a PIN in France. Automatic teller machines (ATM) all take CB, Visa, Mastercard, Cirrus and Plus and are plentiful throughout France. Traveller's cheques are difficult to use — most merchants will not accept them, and exchanging them may involve finding a bank that accepts to exchange them and possibly paying a fee. Note that the postal service doubles as a bank, so often post offices will have an ATM. As a result, even minor towns will have ATMs usable with foreign cards. Exchange offices (bureaux de change) are now rarer with the advent of the Euro - they will in general only be found in towns with a significant foreign tourist presence, such as Paris. Some banks exchange money, often with high fees.
Talk
Yes, it's true: while most people in France under the age of 60 have studied English, they are often unable or unwilling to use it. This is not necessarily linguistic snobbery, but is usually due to lack of practice, or fear that their little-used-since-high-school English will sound ridiculous. Please note that British English, spoken with the carefully articulated "received pronunciation", is what is generally taught in France; thus, other accents (such as Irish, Scottish, Southern US or Australian accents) may be understood with difficulty, if at all. Try to speak clearly and slowly, and avoid slang or US-specific words or phrases. There is no need to speak loudly (unless in a loud environment) to be understood; doing so is considered impolite. French is the official language of France, although there are regional variations in pronunciation and local words. For example, thoughout France the word for yes, oui, said "we" is pronounced "waay." It's similiar to the English language usage of "Yeah" instead of "Yes". In Alsace and part of Lorraine, a kind of German, called "Alsacian", is spoken. In the south, some still speak dialects of the Langue d'Oc (because the word for "yes" is oc): Languedocien, Limousin, Auvergnat, or Provençal. Langue d'Oc is a Romance language, a very close relative of Italian, Spanish, or Catalan. In the west part of Brittany, a few people, mainly old or scholars, speak Breton; this Celtic language is closer to Welsh than to French. In parts of Aquitaine Basque is spoken, but not as much as on the Spanish side of the border. In Corsica a kind of Italian is spoken. However, almost everyone speaks French and tourists are unlikely to ever come across regional languages, except in order to give a "folkloric" flair to things. In Provence, Provençal is most like ly to be spoken, especially along the Riviera. The French are generally attached to politeness and will react coolly to strangers that forget it. You might be surprised to see that you are greeted by other customers when you walk into a restaurant or shop. Return the courtesy and address your hellos/goodbyes to everyone when you enter or leave small shops and cafes. It is, for the French, very impolite to start a conversation with a stranger (even a shopkeeper or client) without at least a polite word like "bonjour". For this reason, starting the conversation with at least a few basic French phrases, or some equivalent polite form in English, goes a long way to convince them to try and help you.
Stay safe
Crime-related emergencies can be reported to the toll-free number 17. France is not a high crime area but large cities are plagued with the usual woes. The inner city areas and a few select suburbs are usually safe at all hours. In large cities, especially Paris, there are a few areas which it is better to avoid. The outer ring of most cities and especially suburbs are sometimes grounds for youth gang violent activities and drug dealing. The subject is very touchy as it may easily have racist overtones. If you are traveling alone, especially if you are a woman, you should avoid using public transportation at late hours especially on links between the city center and the suburbs. Usual caution apply for tourists flocking around sights as they may become targets for pickpockets.
While it is not compulsory for French citizens to carry identification they usually do so. Foreigners are advised to carry some kind of official identity document. Although random checks are not the norm you may be asked for an ID in some kinds of situations, for example if you cannot show a valid ticket when using public transportation; not having one in such cases will result in your being taken to a police station for further checks. In France, failing to offer assistance to 'a person in danger' is illegal. This means that if you fail to stop upon witnessing a motor accident, fail to report such an accident to emergency services, or ignore appeals for help or urgent assistance, you may be charged. Penalties include suspended prison sentence and fines. The law does not apply in situations where to answer an appeal for help might endanger your life or the lives of others. France has a liberal policy with respect to alcohol; there are usually no ID checks for purchasing alcohol (if you look older than 18, of course!) However, causing problems due to public drunkenness is a misdemeanor and may result in a night in a police station until the person can behave themselves. Drunk driving is a severe offense and may result in heavy fines and jail sentences.
Stay healthy
Pharmacies in France are denoted by a green cross, usually in neon. Contrary to the US habit, they don't double as general stores, and only sell medicine, contraceptives and often beauty and related products (though these can be very expensive). Medicines must be ordered from the counter, even for non-prescription medicines. The pharmacist is able to help you about various medicines and can propose you generic drugs. In addition, supermarkets sell condoms (préservatifs) and also often personal lubricant, bandages, disinfectant and other minor medical helps. Préservatif machines are often found outside pharmacies and in bar toilets etc.
Medical treatment can be obtained from self-employed physicians, clinics and hospitals. Most general practitioners, specialists (e.g. gynecologists), and dentists are self-employed; look for signs saying Docteur (médicine générale = general practitioner, etc.). The normal price for a consultation with a general practitioner is 21€, though some physicians charge more (this is the full price and not a co-payment). Physicians may also do home calls, but these are more expensive. Residents of the European Union are covered by the French social security system, which will reimburse or directly pay for 70% of health expenses (30% co-payment) in general. Other travellers are not covered and will be billed the full price, even if at a public hospital; non-EU travellers should thus probably have a travel insurance covering medical costs. Note, however, that, in general, medical fees in France, even when paying the full price, are low compared to those in the United States.
Emergencies Hospitals will have an emergency room signposted Urgences. The following numbers are toll-free: 15 Medical emergencies 17 Law enforcement emergencies (for e.g. reporting a crime) 18 Firefighters 112 European standard emergency numbers. Operators at these numbers can transfer requests to other services if needed (e.g. some medical emergencies may be answered by firefighter groups).
Smoking
Smoking is prohibited by law in all enclosed spaces accessible to the public (this includes train and subway cars, train and subway station enclosures, workplaces, restaurants and cafés) unless in areas specifically designated for smokers. There was an exception for restaurants and cafés, but since the 1st January 2008, the smoking ban law is also enforced. You may face a fine of 68€ if you are found smoking in these places. Smoking is also banned in the Paris métro and SNCF train. Subway and train conductors do enforce the law and will fine you for smoking in non-designated places; if you encounter problems with a smoker in train, you may go find the conductor. As hotels are not considered as public places, some offer smoking vs non-smoking rooms.
Source: Wikitravel.