When leveling I wore nothing but quest rewards and instance drops from instances that I was xp farming in. All the characters matched so all I had to do was look at their mana and health to see if one of them was wearing gear he shouldn't have been. I wouldn't equip the instance drop until all 4 characters had their piece. This kept me from accidentally equipping something and selling my good gear a couple different times. Of course this only works if you are leveling characters of the same class.