I don't speak for everyone, but folks tend to keep their spots to themselves. More of a "do your own research" kind of thing. To get started, I would recommend consulting old maps. Usually, the library has them to view or they have books that contain year-to-year maps. Locating old house sites (on public land!) is a good place to start. Walking through old, unmaintained forests is sometimes a good way to find dumps. Looking at old bridges and walking the riverbed can sometimes yield bottles. There are many ways to get started but you will be hard-pressed to find someone to give you an exact location, in my opinion.