Undercooked pork.
Oh wait, I thought it was what makes moderators sick . Oops, my bad.
I don't know that I had a policy per se. If a person wrote to me saying "ooh, can I be a moderator" I generally asked myself why someone would want to do that.
Usually I picked someone who was here a lot, showed a lot of common sense, was quick to give useful answers and advice, were kind to newbies, and stayed really cool under pressure (didn't fly off the handle often, used a soft answer to turn away wrath, sought first to understand and then be understood, etc.). And once I had a little cadre of mods I took their suggestions for new mods.
It's often not fun. You sometimes have people almost point blank challenging mods, pushing the limits of what's acceptable, then spouting off about free speech or not being constistent. I think the best thing I did was not have too many hard and fast rules. You really had to follow the spirit of the rules rather than the letter of them (I mean, "don't offend Eric's Grandmother" was about the extent of the written rules).
But the benefit is that thousands of people interact here and have a great time. And over time the forums gain a sort of self-moderating aspect that's really cool to see.