The most critical aspect to building community is to help all your members and followers create habits. And habits get formed through consistency.

You need to be consistent in your blog posting, status updates and other forms of engagement or else you'll be fighting an uphill battle.

Earlier I mentioned Twitter chats facilitated by the use of a particular hashtag. This type of event needs to be very consistent in order to accumulate a following over time. Try not to miss a week (even for holidays as they might not apply everywhere) and have the same person consistently leading it to form a relationship with the participants.