For any range of topics, lighthearted to serious, hobbies and games to helping and engaging with community matters. Regarding reach, I mean what ways may be used alongside word of mouth, as I honestly don’t hear people talk about groups they’re in (besides sports/bands) all that much.
It still works if the posters are in places that a lot of the people in town would visit. I’ve seen a lot of small town restaurants/gas stations/feed shops with an area by the front with posters and business cards etc.