10/16 Just returned from a memorable month in France with my husband. Two weeks in Paris, two weeks driving to various locations. A dream come true and memories to last a lifetime.
I want to add however, we did have two events which I feel would help others on their way and it probably fits for most countries.
Stay clear of Hertz. I used Rick's suggestion of booking a car with Autoeurope. I booked a car in the US but needed to change my return location once I was in France. Autoeurope changed the reservation easily but switched my rental company from Europcar to Hertz. I did not realize/know what a difference that would make. The Hertz rental at Charles de Gaulle was horrible, which is the nicest way I can describe it. Just be very careful if you do pick up from Hertz as the integrity of their personnel is low in our experience. Make sure you clearly understand every line item even if you have to ask for repetition of the explanation or a supervisor. The agent who "helped" me ended up charging me for insurance that I thought I had declined. Remember many if not most credit cards you use have some form of insurance for rental cars when you travel abroad. We spent quite a bit of time researching that before we left and thought we knew what we we doing. Alas, not the case. I do speak French but in this case it did not help us.
Booking.com also let us down and I since learned that my experience is not too far from others. So my advice is to look at more than the Booking.com reviews for places you find on that site to confirm the glowing reports you see on their listing. Also know that if you cancel a booking which we did after arriving and finding it unacceptable, you can not give a review for the location because technically did not stay there even though we had to pay a cancellation fee and we did so because of the state of the location.. (That is Booking.com's policy according to customer service who did not want me to talk to her supervisor.)
Our trip was truly phenomenal on the whole. The French people were extremely helpful especially outside of Paris and we plan a return trip in the future.