Tree view.
Clamping down on gratuitous insults of other posters.
Stopping the hijacking of threads. Even this one has been hijacked. some people only want to talk about themselves not about Arsenal. You need more hands-on moderation to delete irrelevant posts.
Invite existing members to post and do a bit of PR on Facebook or Twitter or wherever and when new members join (or old members come up with yet another character) treat them with a modicum of politeness.