Don't rely on search results. This attracts information-seekers. Few of these will become regulars.
Rely upon the three channels you can control.
- Direct marketing. Reaching audiences you already have access to.
- Word-of-mouth. Encouraging existing members to refer others.
- Promotion. Reaching audiences that you don't already have access to.
In the early stages of developing a community, you rely entirely upon direct marketing. You begin individually inviting the first people to join (hold back on other assets). You build a core group of members. Then you invite segments of your mailing lists to participate in discussions too.
As the community moves into establishment, you gradually shift from direct marketing to word-of-mouth encourging word-of-mouth activity. This means increasing the involvement and engagement, and providing an easy means for sharing community activities. There are plenty of tactics here.
Once the community moves into the maturity phase, you shift away from direct marketing entirely and towards increasing word-of-mouth and, sometimes, promotion. This is usually a measurable, campaign-based, process to expand the community or rejuvinate a fading community.
The key is selecting the right channel of growth for your community's stage in the lifecycle.