1. Train your dog to run off-leash in open, un-fenced spaces. There are NO fenced dog parks in Paris. None. Nada. Rien. In other words, your dog should come when called. From what we can tell, Parisian dogs are trained this way from the very beginning, so unless you are bringing a puppy to Paris (who can learn from the locals?), you might want to invest in some off-leash training classes.
2. Train your dog to pee on hard surfaces. There are very, very few grassy spots for Spot to take care of business. Your life will be easier if your dog can pee on the nearest garbage can. I'm not exactly sure how one trains for this... we haven't yet been able to figure it out.
3. Train your dog to ignore pigeons. Pigeons are everywhere here. If your dog likes to stalk pigeons, it will be very difficult to walk down the sidewalk to the nearest non-grassy, non-dog park. Again, this is not something we've had success with.
4. Train your dog to wear a disguise. Well, not really. But if you want to take your dog anywhere that is not within walking distance (and you don't have a car), you will have to sneak him or her onto the Métro. Alas, Parisians seem to ignore this breach of the law much as they do subway panhandlers.
5. Train your dog to be ignored. That is, your dog may be super cute and win the hearts of all passersby back in the States, but this is Paris. Public displays of affection for someone else's dog just don't happen. Unless, of course, you encounter another dog owner. This may afford you a cordial Bonjour, or perhaps just a knowing smile.
When it comes down to it, we're happy that Panda accompanied us on this adventure (if a little stressed every time we let her off-leash and watch her sprint off into the distance). She has forced us outside every single day (and will continue to do so even through what we've been told will be a dreary winter) and sparked conversations with strangers we never would have had otherwise. However, there are aspects of having a dog in Paris that we did not ever consider - hopefully these tips will help others be more fully informed.