Read Your Mails
You are maybe used to the marketing materials being sent out by various companies on your mails. If you are the type who do not look at the mails but instead throw them out the instant you knew what they are, hold yourself a bit before you continue doing so. Look into travel brochures or catalogues that may be included in your mail. These materials can give you exact details as to what you want to know about, like where to go, how much it would cost and who do you contact in case you want to reserve a camping site.
These kinds of information can also be gathered on the internet. But if you already have the marketing materials about the topic, you should read them all and browse through all the papers. There are companies that give out discounts and other freebies, and they usually include such promos and offers on materials like brochures and catalogs.
Have a Look at the Library
It may sound old school, but you may also want to check out your local library for the materials that they have about the matter. It will also be better if you will start learning few French words. This way, when you have reached your destination, it will be easier to locate where you are really going because you will be able to ask people for directions and other matters that may be important to you the moment you are already in France.