You get users. The most important part imo is the regulars who stick around and talk to everyone, answer everything. They make the core of a community and help turn others into regulars.

I used to have 2 small niche forums and there were always 2-5 people that created the bulk of the content (along with myself - I had to post a lot to start and keep it going, I was the first user!). Always making threads, checking in, answering questions, posting updates and pictures.

New visitors would read all that and either never return, lurk or join in. They were passionate about the topics. Giving them special/higher privileges helped retain them for longer, as well, but eventually they just visit less (or leave completely) and someone else takes their place.