Backpacks 

Backpacks may be in three views. Slot, Classic and List Views. 

To change Views, click the small 'gem' near the backpack in the top left hand corner. To 'set' your default container view, go to Main Menu/User Settings/Interface tab.

To select a quantity of 'items' (eg bandages/gold/pots) from a stack, press 'shift' and drag the item. This opens a quantity box to allow you select how many you want. (See the looting information on how to 'change' the way stacks are selected to 2d mode, i.e. drag, and type over qty select.)

Because you can now 'right click' to loot corpses, items fall directly into your backpack. A good way to stop this loot from mixing with your 'normal' items and creating a big mess is to carry a couple of containers of different color, one for your items and one for your loot. Another alternative is to put your 'normal' items, including spell and runebooks etc in the bottom row(s) of your backpack if using grid view, so when you die they stay there.

Note that items such as spellbooks must remain in the main backpack to be able to use them irrespective of whether or not they are in a hotbar (or in the case of a spellbook it needs to be equipped if not in the main backpack).

Runebooks set with a default key may now be accessed from a hotbar, so all runebooks may be placed in a bag within your pack and to recall to the default location target the book in the hotbar.

Other items such as a aids, reagents, dagger, petals, bag of sending, scissors, bandy talismans, spare jewelry, weapons etc may be put in your items bag or bottom rows. All items with a 'use' such as pots, petals, bos, runebooks etc may be dragged to a Hotbar  to 'use' and can be accessed from these hotbars with one click. 

With all your 'regular items' out of your main backpack or in the bottom, it is then easy to see the loot as it is picked up. This may be dragged between monsters into a loot box to 'keep things tidy' which you can sort after hunting. I recommend you leave your gold pile in your main backpack to avoid having to find it in your loot box if you get heavy and need to send it to the bank quickly!

When you log in it is a good idea to open your main backpack and any other containers inside any other containers such as an 'item bag' to ensure the contents refreshes. Until refreshed you may not be able to get the item in the hotbar to work. 

Note that 'backpacks' and other containers within your items bag (if you use one), may also be placed in a hotbar. For example, my Paladin carries a few slayer weapons around but I do not wish them to be on equip macros as they are used rarely. So I have a weapon pouch and this pouch is on my 'items' hotbar. You can click on the pouch on this hotbar and it will open as a regular backpack so you can select from the pack to equip without using your main backpack.