Exactly how should I do it? When I group with someone doing quest, sometimes a small window pops out and I can choose need or greed. I understand that need equals roll?
But in other cases, for example, there’s a chest. Do we split? Or a mob has a quest item. How do you normally deal with it?
It sort of depends on the group, and whatever rules have either been established or are established when something drops that people might need.
Personally, for chests, while most people seem to /roll, I always just type out “pass.”
If you don’t actually need it for your present characters actual immediate use then greed it.
This is the best way to play unless the rules are established different from the start of the dungeon.
Make sure if a bind on equip (BoE) drops in a group to always suggest everyone needs for it, sometimes you will run into some people who will attempt to take advantage of you.
Regarding quest items: they have a chance of dropping when it’s your turn to loot on the “round robin”. If you loot the body but don’t pick up the quest item, everybody else on that quest will have the option of picking up that quest item.
However, because the quest items fall on a round robin, it’s generally easier for every person to loot quest items for themselves as they fall. If one person finishes the quest faster than another, courtesy is to stick around until the other person is finished, too. It’s easier than trying to ensure everybody gets 12 bandanas at the same rate.
Need what you need, greed what you want.
Chests are usually done on a /roll basis.
If you’re grouped with somebody and they are on a quest and you aren’t, be sure to loot mobs that show you have loot on. If you don’t loot, they may miss quest items if you don’t.
Greed it unless you need it
on greens greed unless you need it if its a boe epic the group should have decided on it what to roll before you started but i can assure you if its a pug someones gonna need it even if they wont use it
chest and other things in the world , I guess the easiest and fair way to do it is /roll . Its basacly the same as greed if you think about it .
Depends on the group. Me personally I never roll need. I roll greed if I want it or I pass. Same for chests. And I only roll for things my current character could use.
I won’t potentially cheat a team mate out of an upgrade for one of my alts. Or if we are running on “Free for All” I’ll offer team mates free upgrades if I find one for them.
That’s just me though. I like to believe I’m super nice. 
Edit: Grammar.
Just need all, feign ignorance, and then once your server rep is trashed enough thst nobody invites you, server transfer as Blizzard intended.