However, as something of a career moderator (I'm trying admin for the first time!), I'd like to point out that a truly good moderator shouldn't need a manual - if nothing else, they should have a good 'sense' of what to do in most situations.
Of course, each site's unique foibles and quirks will need a little explaining, but I'd expect a good moderator to know the difference between posting plenty and just spamming for the sake of it, for example. I'd certainly expect them not to indulge in it!
The important thing when appointing anyone to represent you and your board (because let's face it, that's what your staff are doing) is to trust them. When my current project finally gets going and (fingers crossed!) reaches the size where myself and my partner in crime can't handle it alone, I will only give moderator access to someone who I have observed on the forums for long enough to trust that they are capable of doing the job.
Occasionally, there won't be anyone fitting that description, which can be a problem. However, I'd maintain that you'll suffer fewer headaches from leaving a potentially troublesome post up for a few hours while you attend to 'real life' than you would from appointing an unsuitable moderator.
Rules are all well and good (and please don't get me wrong, as rules go, the suggestions in this thread are fantastic), but even if you have the best rules in the world, it doesn't guarantee that your team will follow them.
Thank you Kathy, thanks a lot. I've been looking for exactly something like this for a week now. I am not as expressive or thoughtful as I want to be when trying to write something like this, so this should help me compile my own mod manual without seeming scatter-brained, heh heh.
EDIT: Also thanks to those of you who shared your own mod manuals and thoughts on the subject, I'll be incorporating ideas from those as well.
Kathy, I've been working on putting a Moderators Guidebook together myself lately, and find it a bit daunting to codify everything in a succinct document. Thanks for the post -- this is a great starting point for me!