Yeah, questions are good! Also, I use the tagging system to tell jokes, and people seem to respon well to those.
Replying to comments is also important - I try to do that as often as I can. Sometimes, there's not much I can say except "thanks" and then I might skip answering, but if a commenter has asked a question or something, I do take the time to reply.
Another thing that I feel works is that I post a thank-you image on the walls of new subscribers - it's partly because, well, I'm thankful they subscribed, but it's also partly a signal to them that it is 100% okay to talk to me, as some people are a bit hesitant.