Hitchhiking is great. It trains you in the following aspects.
getting to know your people
Some creative ideas for hitchhiking are listed in a book of Rüdiger Nehberg. One is, to have some things like a teddy-bear at your package, because no bad man has such things. Or something extraordinary, where the drivers would think: "Wow, I wanna know more about this guy!"
Knowing the Autobahn system with its infrastructure of rest areas. Knowing about how roads lead to different areas. This is very relevant for finding the right hitchhiking spots. You have to know about it, unless you are willing to waste hours and hours in the painful process of finding out.
I usually talk with people about stuff that they know very well about. For example their job or a bigtime hobby or something important that is going on in their lives at that moment. So they are experts and I can learn a lot from them!