Just find yourself a decent Guild that doesn't PUG unless they really have to. If its a decent enough guild you should be able to find FP's to do all day long with out ever PUG'ing and getting ninja'd. Before joining a guild I saw plenty of ninjas but now dont see any at all. The guild should have the rules set and all members should follow them.
The system I follow is:-
Need - only if i am going to equip it right there and then, or if it for that toon's craft.
Greed - use for companion
Pass - if i cant use it at all, no point in selecting greed if your just going to sell the item to the vendor, the price you get for the items is practically nothing So I just don't bother. If items held any real value at the vendor, then Id change to greed but currently no point.
Alot of people may disagree with the above, but as for guild rules it keeps the peace.