The guild has an 8 tab bank, the maximum size allowed by Blizzard. Depending on your rank, you have access to different tabs.

Any item worth over 5g is welcome in the bank. Items removed from the guild bank are never to be sold. Council members may remove items to sell, but the proceeds must be put back in the guild bank. 

If you take items out of the guild bank, put items in to the guild bank. You get what you give.

Give according to your ability: Everyone claims to be poor, but you know what you can give. Some people have given in excess of 100k to the guild. For a level 60 toon that is a lot, but it might be the same as a level 10 toon giving 1g.

Only take out items you can USE & NEED on the toon you are making the withdrawal on. The bank isn’t for your alts or friends who aren’t in the guild, its for guild people. If you need something and don’t have permission, ask a council member.

If you see something you need, and you cant access it, send an in-game mail to “Engagement” and ask specifically for the item. Say something like “Tab 3, row 8, item 3, along with the name”.