Basically, throw out all quest items. That's a great start. I'd recommend buying a rare [but that has nothing to do with organizing the bank]. Throw out holiday items and things that you dont use [such as your beers. You may as well keep the 'rarer' ones, i.e., the one's you can't buy in a store, but throw out your dwarf stouts, etc.] Then once you've cleared it out, put everything in groups, such as runecrafting, crafting, combat, etc. That's basically it.