2. Maintain a proper registration system
Even if you allow users to participate using aliases or nicks, the moderators ought to know their identities. This is significant if anyone is to prosecute those who have expressed themselves in a legally prohibited manner.
There are several ways to register users, for instance through a Facebook account, Disqus, aID and others. We find it difficult to recommend one system rather than another, but will advise you to allow some time searching for the system you find best.
Also, be aware that some media outlets - Nettavisen, for instance - have created systems of their own, as they do not find Facebook secure enough, due to its possibility for fake profiles.