Community managers can either tweak the environment (the platform, the identity, the purpose) or stimulate the participants (direct interactions with members).
When you’re just getting started, you’re going to rely upon direct influence. This is you interacting with a small group of people and getting them involved in what’s going on. You’re going to personally invite members to participate. It’s hard work.
As time progresses you’re going to rely upon tweaking the environment. You’re going to toy around with game mechanics, tinker with the platform and develop a more automated process for converting a newcomer into a regular. There are many ways to do this.
But which of these do you use, and when?
If your community has a clear problem (lack of members, activity etc…), directly contacting members is the path to go. If you want to improve upon something that’s already working in the community, tweak the environment.