My 2-cents:
NEED ROLL: Let people know that you're going to roll NEED. I consider it polite. If you don't, people might assume you're a "ninja looter", especially if everyone rolls greed, and you roll last and "need" the item. Just looks bad.
GREED ROLL: Greed roll everything that isn't bind-on-pick-up - unless you can disenchant the item if you can't use it. I'm not an enchanter, so I pass on BOPUs, unless they are better than what I've got and I can use them.
PASS: I pass on items if they can't be used by my class, and someone in the party needs them. Or, if I feel particularly guilty for failing the group earlier in the instance/quest, I'll pass a few items to ease my mind.
