Space Saving Tips
There are several helpful tips that you can use to clean out your
bank, without risking any items that you may need later on.
Food
Having both cooked and uncooked food of the same type (like both
cooked and uncooked Lobsters) is useless unless you're training
cooking at this moment.

In this picture, I have both cooked and uncooked Lobsters. I only
have 52 uncooked ones, so it won't take long to cook them, and with
the use of the "cook-all " option it's even faster. Use a bit of
time now to cook them up so they're ready for when you need
them.
Worn Items
Some items are better off to be worn, rather than sitting in your
bank.

small amounts of money. I could throw my Rubber Chicken and Yo-Yo
away since I could easily get them back from Diango in Draynor
Village. They're only fun items that you can show off, and it also
included Bunny Ears and Scythes. Zombie Heads can also be obtained
by digging in the Lumbridge Swamp with a Spade.
Tiaras & Talismans: You can craft your own Tiaras used in
Runecrafting, but you'll also need a Talisman to make them. You may
even be able to buy some from other players.
There is also no point in owning both Talismans and Tiaras; just
convert your most used Talismans into Tiaras, and throw out the
Talismans that you never use.
Equipment: Items that are used in skills (fishing equipment,
farming items, moulds and crafting equipment, and items bought from
the general store like buckets or tinderboxes) should just be
tossed out, unless you use them very often. When you're finished,
just throw them away.
Random Items: This includes items like broken arrows, broken armor,
burnt food and other useless items. Just throw them away, because
they can't be used. The exception is the Rusty Sword, which can be
given to the Tindel Merchant in Port Khazard to identify. He'll buy
them for a decent amount of money.
Duplicates: Don't keep multiple items for the same thing. If you
have an Iron Hatchet and a Mithril Hatchet, either drop or sell the
Iron one in a General Store. It's pointless to have multiple items
of the same type.
Also, it's best to keep only 1 or 2 amulets of different kinds,
such as Diamond (for Freeplay) and Dragonstone (for Members). Try
not to keep both enchanted and unenchanted amulets of the same kind
either.
Important items
These items shouldn't be thrown away just to save space. You could
drop them during a drop party or give them to friends.

Here are some items that should never be thrown away. This includes
the cash, mining and woodcutting equipment (below mithril can be
thrown out) and Runes.
Runes: Usually it's safe to throw out Runes if they're in a small
number, unless you're going to use them. Only keep Runes that you
need; throw the rest out. Runes such as Law, Chaos, Death, and
Nature should be sold rather than thrown away.
Holiday & Rare Items: Any holiday items such as Party Hats,
Santa Hats, Pumpkins, Easter Eggs or Masks should never be thrown
away (or eaten!), as they are worth quite a bit of money. Random
Event items such as Frog Masks, Mime items, Lederhosen, and Camo
should never be thrown away. Equipment above Mithril, or trimmed
armor shouldn't be thrown away either
Skill Items

Many items can also be better used for skill training, so rather
than letting them sit in your bank, use them up!
Gems: Always cut your gems up, since they're difficult to sell
anyways, and can be used in Jewelry.
Feathers: Use these in either fishing or fletching, rather than
letting them hang around in your bank.
Rune Essence: Try to make these into useful Runes or merchant
them.
Logs: You can use these in firemaking or fletching, or you could
sell them. Usually, the lower-level logs can be burned or fletched,
while it's better to merchant the higher ones like Yew or
Magic.
Herbs & Potions: Herbs should always be identified and made
into potions (if possible). Low-level potions like Attack or Stat
Restore potions could always be emptied out and re-used.
Seeds: Don't keep all of the different seeds for farming. Only keep
the ones you use, and just toss (or sell) the ones you know that
you aren't going to use.
Quest Items And wise old man
Most rewards for Freeplayers aren't very good, but if you have any
doubts, it may be a good idea to visit the Wise Old Man in Draynor
Village.

He will identify your quest items and he will help determine what
you should and shouldn't keep.
Silverlight: the only good use for this weapon is to kill demons,
as it is equivalent to Rune when fighting them. If you have a rune
or Dragon weapon, just toss it. You can buy a replacement from Sir
Prysin in Varrock Castle for 500gp.
Blurite Sword: this has no use, and unless you don't have a better
item, just toss it.
Amulet of Ghostspeak: Once you're finished the Restless Ghost
Quest, this can be safely thrown out. You can get another one from
Father Urhney in Lumbridge Swamp.
Amulet of Accuracy: Only keep this until you get a better enchanted
amulet.