World of Matticus has a good post on Structuring Your Casual Raiding Guild. Here are a few snippets I found interesting. I think that lack of some of these positions contributed a lot to the dissolution of my raiding guild. It was largely a one-man show so when he quit it was over.
Choose officers based on what your Guild Leader lacks. “The bottom line is that these are individuals that your Guild leader can trust and depend on.”
(Raid Leaders) “call for what it is that they want to happen. They might want a sheep on square, a misdirect on skull, or a trap on circle. They donít care who does it as long as itís done. They have delegated duties down the chain of command.”
For loot distribution, “No matter what system is used, always ensure that Officer discretion can come into play at some point.”