Pronunciation is mostly precisely expressed through IPA, the International Phonetic Alphabet used by linguistics. However, it's probably pretty likely that most people reading this don't already know IPA. However, if you're planning extensive language work, it's a great idea to learn it as it provides a precise way to learn the pronunciation of a language. Most of the pronunciations, thus, will be explained in terms of both IPA and approximating them in standard English.
If some letter isn't mentioned in the course of this article, then just assume that it is pronounced the same as in English. The two languages have a lot in common!
All that being said, it is very difficult to pick up subtle differences in pronunciation on an entirely written guide. The best way to learn pronunciation is, as always, by working with native speakers. This should be considered an imperfect substitute for this, and not a complete alternative. All else failing, try to find recordings of French speakers saying words and see how they line up with the spelling of the words.
French has many dialects, with many variants on pronunciation, from Sub-Saharan Africa to the individual neighborhoods of Paris. So how can there be one single way to pronounce French?
The “standard" dialect is Parisian, that is, from Paris. This is the one that will be described in this article. However, if you're traveling somewhere other than Paris, then expect to hear something a little bit different from what you'll be reading about in this article. Most French speakers can at least understand the Parisian dialect, however, so don't fret.
Also, keep in mind that these are general rules, as it it impossible to avoid exceptions in a language! There will be situations when these simply won't apply and you'll have to memorize the pronunciation as learned from a native speaker.
Probably the most difficult—and most important—thing to master in French are the vowels, so we'll cover that first.
Vowels may be modified by a number of accents. The accent grave, à, acts to shorten the sound of the vowel. This is most common over a. The accent aigu, é, acts to lengthen the vowel and make it sound more open, for example été or répété. This is most common over e. The circonflex doesn't strictly modify the sound, and is there primarily for etymological reasons. It is found mostly over o and a.
The vowels are divided into two main types: hard vowels and soft vowels. The hard vowels consist of a and o. The soft vowels consist of u, i, and e.
From here, a vast array of vowel sounds emerges, and frankly, there is not space to describe it in this article. Try just pronouncing vowels and vowel clusters in the English manner, as they are largely quite similar, but with the following rules to guide you:
Vowels may be nasal, which means, well, they're made to sound more nasal. While this may seem really obvious, especially if you're familiar with the usual caricaturization of the language being one that is entirely nasalized, it may also be difficult for English speakers to approximate and recognize for themselves.For nasalized syllables like en, dans, sans, on, un, brun, or hein, try integrating a vaguely grunt-like quality into the pronunciation. You've probably picked up a pattern by now: most of these vowels or vowel clusters end with an n. Use that as a marker to guide whether you nasalize the syllable or not.
Certain situations call for the syllable, and specifically the vowel, to be lengthened. This is almost always in cases where that particular syllable is stressed to give it that extra emphasis.
Another distinctive feature of French is the schwa, known as the mute e or the muet e. It is a highly unstable feature of French, sometimes making the /ə/sound, sometimes merging with other sounds, or sometimes simply not pronounced at all. As an e at the end of a word, it tends to simply be ignored, such as in porte or table. It may also be pronounced when it is represented by an é or ée at the end of a word, such as with past participles. In one-syllable words, it is often the only real sound, such as in ce, de, or que.
For vowel clusters, the trema accent plays an important role. The trema is generally placed on the second vowel of a cluster, and acts to force the two vowels to be pronounced distinct from each other. Think of the Anglicized word noël.
However, not all vowel clusters have tremas, as is obvious from many of the above examples. In such situations, the glide plays an important role. This is not represented by any particular symbol, but it sounds something like our English y sound being placed between the vowels, though not quite as conspicuous. In such vowel clusters, is, ous and other long sounds dominate, while the shorter sounds like the mute e are left unstressed. Examples are nier, louer and tuer.
Compared to the mess made by the vowels, the consonants are comparatively easy. They are mostly the same as in English, especially when it comes to imported words like camping. So, it is only the differences that will be highlighted in this section.
h comes in two varieties, aspirated and non-aspirated. Aspirated h is the same as with the standard h in English, like our hamburger. Non-aspirated h basically means that you ignore that the h is even there, which somewhat confusingly in French includes hotel, hopital and hockey. There's no real rule to see which one will be used, so this will have to be memorized. Fortunately, it doesn't crop up too much in French.
Consonant clusters with p, most commonly ps or pn as in psychologie or pneu, pronounce the p separately. This may seem awkward to English speakers. However, the ph makes the f sound as in English, such as in physiques.
q never makes our kw sound, as in the English quest. Rather, it always makes a hard k sound that we have in English. This may be observed in the French cheque.
ch in French never makes the hard English channel or chore sound; rather, it is always soft like our sh sound,/ʃ/, such as in château.
th also does not make our English the or three sound. Instead, it more sounds like a t sound with a slightly aspirated h following it, such as in the French Théodore.
r is a tricky one, as it can vary considerably from speaker to speaker even within just the Parisian dialect. Your best bet is to pronounce it with a sort of slight growl, the /ʁ/ sound. Practice with r-rich words like préfère.
g and c may be either hard or soft; that is, like the English go/gem or cat/Cecile. This depends on whether either a hard or soft vowel comes after it, which have already been described. For aesthetic reasons, the French often like to change whether these consonants are hard or soft despite wanting to retain the hard vowel immediately following it. For c, this results in a cedille accent to be added to it, or “c squiggle" as many French students refer to it as. For g (and rarely the c), this results in an e being inserted afterwards, such as in the irregular conjugations of manger, ex. mangeons. The reverse, an intentional hardening of the consonant, does not occur.
This is another distinctive feature of the French language. As the last letter of many French words, the consonant is left unpronounced—the default pronunciation. This functions as a sort of latency, as if a word with this feature is followed by a word that begins with a vowel, the consonant is pronounced and the two words slurred together as one. For example, deux ans or trois années.
This is rather like the reverse of the liaison. If the first word ends in a vowel and the second begins with a vowel, then the two words are smushed together, the soft vowel of the two disappearing and the hard vowel being pronounced. The most common occurrence of this is arguably with je and any verb that begins with a vowel, for example j'arrive, je m'appelle, and others, or with de, rendering such constructions as d'un or d'une.
Sometimes, this is even extended in colloquial speech to erase a soft vowel entirely. Je ne sais pas is often rendered more like je n'sais pas, or je dors like j'dors.
Stress in the French language does not change the literal meaning of a word, but it plays a very important part in getting across subtle meanings and connotations, as in English. Again with the fake French accent, it is highly exaggerated, highly stressed—and is quite often the reality of how people speak! It plays an important part in sounding appropriately “French," though by no means should you feel pressured into changing your entire persona around this.
For More Information
Wikipedia has an excellent article about French phonology, albeit one that is largely geared toward linguists rather than actual students of the language.
About.com's French section has extensive audio files, activities and lessons specifically geared toward bettering your French pronunciation.
Otherwise… as previously stressed, your best resource is just a native speaker. Listen to French music, or, next time you watch a movie, turn on the French dubs! The more you hear French, the more you'll catch on to the sound of it–and pronunciation will come naturally. It won't just be a mess of rules to memorize.