1. Ketchup exists in Paris. It's here, you can get it, heck I've even seen Parisians using it (not many but some) however, mustard and mayonnaise are much more commonly used. I have yet to go to a restaurant that didn't have ketchup when we wanted it and in fact, every time we were in a situation where we ordered things you would want to put ketchup on, they brought it out to us. Aside from this, you can also buy good ol' Heinz 57 at every grocery store I have been to.
2. Speaking of mustard and mayonnaise, I feel they need to be defended a bit. If you are anything like me, when you hear that the French put it on everything, you think of the French's mustard and bottles of mayonnaise you get at the grocery store. That's where you and I are wrong my friends. The mustard and mayo here is like an art form, I have seen more flavours, textures and colours of these items since arriving here than I new existed. In fact after a quick count, we currently have 5 different types of mustard and 2 different types of mayo in our fridge right now...and they are all awesome (I'm not a big fan of the blue cheese mustard, but Julia likes it). So yes, they may put it on everything, but come here and try some of them and you will want to as well, they are delicious.
3. Pain au Chocolate...delicious. Croissants...delicious. Fresh baguettes...delicious. There are more boulangeries (bakeries) in France then I have ever seen (we have 3 within a 5min walk of our apartment), and they are all awesome! One of the coolest cultural observations I have made is watching the Parisians who go and buy a baguette fresh from the bakery and eat it as they walk home...nothing on it, just a fresh baguette...amazing! I tried this once and felt like a tool, but it tasted great. The bread is literally sooo good that you don't even need to put anything on it.
4. Meals are serious business, respect them. I, and most North Americans, have what the French consider bad etiquette. Our culture is more apt to take our time enjoying a coffee or drinks with friends than to enjoy a meal. This is not the case in French culture. Drinks are something that adds to the meal experience, but they are no more than that. The meal itself is the event that you would invite your friends to, and you would be expected to chat and savour the meal. In fact, I would say that if a meal lasted less than 1 hour in France it would be considered a failure.
5. They do eat uncooked hamburger. this one is completely true, and if you order a hamburger and you are used to North American style burgers make sure you order it "Bien Cuir". I cannot stress this enough, BIEN CUIR! It's the equivalent of well done, and it will prevent you from receiving a raw chunk of beef that flames may have touched at some point on its journey between the kitchen and your table.
Please keep these food pointers in mind and I will be back soon with some more observations.