I'm not exactly a top-tier contributor, but my writings here tend to get positive responses, and the reason I don't write more is chiefly lack of ideas. One thing I'm doing is resolving right now to try to write more on LW; another is resolving to be willing to post a broader variety of things until I actually get some negative feedback that I should narrow.

But as far methods external to myself, I wonder if something like a topic of the month could seed participation. Maybe do posts with discussion questions--I actually really enjoyed these on the Superintelligence reading group posts.