I would start out with policies.
First - I would reiterate board rules and make sure moderators know they have to follow these just as closely. I would explain why each rule is in place and what enforcement (if any) would be used against someone who breaks these rules. I would explain the policy behind enforcing rules on people, how many verbal warns are allowed before an actual one, where to post about any action taken against an user (if there is such a place here), when to suspend someone and how long. In my opinion, these guidelines should be in place so that every moderator works in a similar way - it shouldn't be easier to get away with something with one person than another.
I would also discuss expected behavior. Staff should be held to a higher standard, and those standards should be defined. Staff should also talk to members in a certain way, post in a certain way (for example, if they've been drinking, maybe they shouldn't post), etc. People, but especially moderators, will be respected if they come across coherently and with good grammar. If a moderator comes into a thread saying "omg you idiot this hasnt been posted in in two months i am closing it k thx bai", I can promise you, members will probably respect that person less. At least, I would.
I would discuss the privacy policies - what is allowed to be discussed with the members, and what isn't. Staff shouldn't be able to tell regular joes that they are being looked at to moderate, that other members are being warned for particular reasons, that the staff are throwing a SUPER SECRET party and that they want to surprise the members. Some things need to stay secret, this should be defined and communicated to moderators, otherwise some will tell people things without even thinking about it.
Of course, general guidelines such as how active one has to be and how they deal with confrontations should be mentioned. Also, how they deal with actions other moderators take. On the boards I've worked at, a lot of teams would fall apart because moderators were tearing each other apart in public. Once we created a policy to get each others back in public, and discuss the issue privately or in the staff forums, things started running a lot more smoothly.
Hmmm... what else. I'm trying to remember things that were covered in my policy thread. ;)
I would probably end with a quick tutorial on how to suspend, warn, sticky, close, etc. Because all moderators should know this, and having it all in one place rather than having them ask people would be handy.