I'd suggest talking to friends about it, maybe you could get them excited about doing that too. If that's not the case, I'd try and find some local outdoor equipment stores, you could post a flier there or ask if there are any upcoming hiking events/trips someone is putting on. It might not be hiking the entire Appalachian trail but it'll likely be something that helps you get involved in the hiking community and meet people who are interested in a similar trip. Also, shorter hikes would help to prepare you for such a long excursion and help you decide if you really do want to do it or not.