French Expert? No. But here are a few things I have learned and have been grateful to know while traveling in France.
Don't smile at people on the street. When Adam told me about this a few months before we left for France I was kind of floored. In the United States, people usually smile at each other on the street to say, "you're cool, I am cool, we see each other and now we will leave each other alone; right?" In France, people may stare at you, but they generally won't smile, because a smile would be stepping into your space. They might think you want something or maybe that you're hitting on them... On the other hand, if you go into a shop, restaurant, or up to someone to ask for something, it is very rude not to acknowledge them first by saying "bonjour." After all, you are entering their space.