Before I bought my van, I got some advice from a friend of a friend (James) who had travelled with his wife and child for a year around Europe.
One of the best tips was to use books to find 'aires' as they're called in France where you can fill up with water and dump grey (shower/sink) and black (toilet) water and often also plug in to an electricity outlet for a small charge. Note that camperstops are available all over Europe, not just France, but in some countries like Switzerland and Croatia, they're as expensive as a lot-end airbnb room e.g. 30-50 Euros per night!
Some official places are free, and I don't always stay in official places, but sometimes you need services like electricity and water. Usually when I have a friend along, we wild camp.
I use an app called 'Campercontact' and you can find out more at campercontact.com. The app is better than books as you can filter for places with specific features like 'grass' or 'has electricity' and cost etc and then auto plot a route and save your favourites on a route. It's also way better to have an app when you're navigating solo. My cat is not the best navigator unfortunately.
