The rules under which moderation takes place should be easily and publically accessible, as should the names / nicks and contact information of all the moderators.
Moderation should be consistent and within the rules. Should a situation arise which requires the rules to be amended or added to, this should be discussed amongst all moderators to ensure a shared understanding is reached, before then publically documenting the amended or added rule(s), and the reason for the change(s).
There should be a sufficient number of moderators available to handle any situation that may arise, whatever the time of day. Internet drama can happen very quickly, and the longer the delay before a moderator steps in, the greater the chance that things reach a community-destroying stage.