Who Should Read This Guide
If you're a nonmember, then you might want to read this, since you have so less bank space. Otherwise, if you're a member, you don't really have to read this, because you have already got the entire bunch of bank space available to you, and therefore, you will probably never run out of bank space to use, unless you use it in a careless way, of course. Well in either ways, if you're running out of bank space, then this guide is for you.
Starting Off
First of all, you should have a good bank, with no noobish items or anything similar to that. All that does, is just crowd up your bank, and waste your precious space, which should be available to you at all times. It can be a real pain sometimes, when you want to store an item in the bank, and you have no bank space available to you. This guide was written in order to help you clear your bank space, and possibly even organize it.
Managing Your Bank
Food - If you have a bank with so much food, and you don't themit at all, either sell them to a player, or to the general store, or just go into the wilderness and use it all up. You'd be surprised how much food you use up when you go PK'ing. Otherwise, you could try going on Kalphite or dragon trips, if you're a member. Those help eliminate some of the food, as well. If you are already a high level player, and you still have shrimp, meat, chicken, herring, sardines, or food that heal less in the bank, either drop them, sell them, or randomly give them to some noob, who could really use the extra benefit.
Equipment - This is probably the simplest one of them all. Just equip as much of the stuff as you, if you don't mind having a lot of weight. As for the rest, try putting as much of them back in the bank, as you can. Otherwise, sell the equipment that you don't need, or give it away for free, if they cost under 5K.
Quest Items - You can get back quest items fairly easily. You can get Silverlight again, from Sir Amik Varze. But you can't get the Blurite Sword back, however, quest items don't give many bonuses at all, with exceptions of some of them, so you might as well just throw them out.
Holiday Items - Don't worry about these, as you can just drop or destroy the ones that can't be traded, like Yo - Yo's, Rubber Chickens, Zombie Heads, Wooly Scarves and Hats, Bunny Ears, - etc. But do not throw out Santa Hats, Christmas Crackers, Party Hats, Easter Eggs, Pumpkins, or any of those holiday items from 2001 or 2002, because those cannot be obtained back, and if you lose them, they are lost forever. Plus, they cost millions now. For the rest of them, you can obtain back, so you might as well throw them out. Holiday items are basically just like toys, like the spinning plates and toy horsies. They are exciting at first, but you get bored of them eventually, which then, at that time, you should usually think about throwing them out. They can empty out a lot of bank space, if you have a lot of them.
Rune Essences - Either use these to runecraft runes, or just simply sell them. A good place to sell them, is the East Bank in Varrock, where the essence mine is just south of there, and many people buy essences there. Just be sure to sell them for 30 each, as then, you will have earned much money, if you have a lot of them, of course. It may take you a while, if you have something like 1K essence, so you also trying selling 500 - 800 of them, and runecrafting the rest, making it easy for you.
Potions - These are a major bank space taker! You can have many types of potions, and different doses. Potions come in doses of 1, 2, 3, and 4. Don't forget, that if you drink a potion, then it is no longer a full dose, so if you drink a 4 dose potion, there will be only 3 doses left. Now you may not realize this, but now, it is a whole different kind of potion, which means it will no longer fit in with the 4 dose potion! To manage this, try mixing them. If you mix a 2 dose and 4 dose, you will get 2 of 3 doses potions. If you mix 2 of 3 doses potions, you will get a 2 dose potion, and a 4 dose potion. There are also other combinations, that you can try out. Try to have either a 3 dose, or a 4 dose, rather than a 2 dose. Or, if you really need space, just have 3 dose potions, which I think are the easiest to make.