To learn conversational French, or casually spoken French, in other words, you need to possess both an intermediate speaking and oral comprehension ability in French.
What this means is that you can place a lower priority on most of the finer points of French grammar, from verb conjugation, to the use of the correct prepositions and articles, subject-verb agreement and all the little details of the language. Of course, this will mark you fairly obviously as a non-native (and from the specific mistakes you will make, an English speaker). However, conversational French is about communicating, not about perfection, and if you will learn to accept that you will make many mistakes, you can begin having meaningful conversations with native French speakers fairly quickly.
An analogous example in my own life is working with several Filipino men and women. Most Filipinos are taught English for years in school, though not at home, and they have a lot of exposure to English-speaking media. They make some word choices that sound strange to native English ears, and pick the wrong prepositions at times. Yet their accents are good, their vocabulary is broad, and they approach speaking and writing in English with absolute confidence, so there is no problem at all for English speakers to understand them.
If you want to become proficient at conversational French, these areas should be your priorities:
- Working on your French pronunciation to improve your French accent.
- Increasing your intermediate-level French vocabulary
- Listening to how native speakers talk amongst themselves – the cadence, slang, and word choice. The SmartFrench line of software and audio CDs is probably the best approach out there right now for understanding casual spoken French.
- Listening to casual French media – try French radio programs, pop songs, TV shows and non-serious French films (to make sure the language is casual and not “literary”).
- Practicing with native French speakers – once you attain a certain level of proficiency, this is the “holy grail” of improving your conversational skills. There are several popular French language exchange programs online where you can practice speaking with a native French speaker who in turn wants to learn English.
Many language learners are uncomfortable with making mistakes as they speak, and they hesitate too long in trying to conjugate a verb or find the perfect word choice, and they slow down the entire conversation and sometimes get it off-track completely.
You would be amazed at how well you will be understood if you speak clearly and with good pronunciation. You can always work on improving your grammar later, but for now, learning to comprehend and speak casual French at a natural pace is the most critical thing you can do in order to improve your conversational French speaking ability.