So you wanna get teh fat lewt?
First of all, when you join the guild, ur a trial for 2 weeks, meaning all players ranked higher get priority on loot.
All member ranked players usually roll equally on an item from a 10-man instance. However, if a player allrdy got an epic from Karazhan, he can't roll.
lets say a player has wicked witch hat, and the T4 head drops. that player cant roll on the t4 if the other player has not karaloot/arena gear. Even if that other player had spellstrike, he would take the t4 on normal conditions.
Depending on who leads the raid, Veterans ranked players can take the loot, if they thinks its fair, at anytime.
A new thing we also look at is how buffed u are, and how active.
If ur more buffed than the others, this will definitely increase your chances for getting loot!