Players are put in an ordered list, usually based on a random roll (although some have made attempts to translate the order from a pre-existing loot system). Multiple lists may be used (see below for discussion).
When a new player needs to be added to the list, it is possible to let him "roll in," or simply insert him at the bottom of the list(s).
When loot is dropped, the person who wants it and is nearest the top of the list wins the loot and goes to the bottom of the list.
Players who are not currently in the raid do not move up or down in the lists.
If no-one wants the item, it is up to the guild to decide what to do with it