Any of the better guidebooks will give you an acceptable introduction to conversational French. Study the guidebook before you go, and have at least a few key phrases memorized. I found the French to be a very friendly people. It is, however, a totally different culture than what most of us are used to. Some aspects of Paris are those of any big city - pushing on the subway, etc.
BonforXXXX greetings are also farewells.
Tipping of cabbies, doormen, etc is pretty much as anywhere else. Some of them are simply ceramic latrine trenches. These have a place to park your feet, and you squat over the hole. The flush valve actuator may be one of billions of types, but is usually the thing about 3 to 4 feet directly above the hole, attached to the wall, regardless of what this may look like. Simply push, pull, twist, pound, and so forth until something happens.