Money making guide/Grand Exchange Merchanting

Short-term Merchanting
''If you see an item beginning to rise in price, buy it. Wait a few days, and once you see that the price begins to level off, sell it.''

Uncut Gems
Most uncut gems are very unstable in price. Find a good time to buy them and buy them in bulk. It's a good idea to keep them for a couple of days and then sell them back. Players usually make a 5% to 10% profit if successful. A good tip is to browse the RuneScape home page and check the Grand Exchange Database. Check which type of jewellery is going up at the moment and which is plummeting.

Amulets
Some amulets, most notably the amulet of power, are always fluctuating in price. For example, one could buy it at lowest price today and sell it for highest price tomorrow depending on the situation.

Long-term Merchanting
The following items are stable, but may skyrocket once or twice a month due to merchanting clans, doubling in price. Beware, it may drop immediately the day after.
 * Druidic mage hood
 * Druidic mage top
 * Druidic mage bottom
 * Air talisman
 * Infinity boots

Expensive Items
These items can usually be bought for a little less than the market price and then sold for a little more than the market price.
 * Saradomin armour set (l) (buy this for 25k under market price and sell for 25k over market price)
 * Raw or cooked swordfish
 * Raw or cooked lobster

Merchanting Clans
Since the Grand Exchange was introduced, many people have created merchanting clans, or merch clans. What these clans do is have everybody in the clan buy a certain item (usually the current clan name) at maximum Grand Exchange price. This will usually cause to price to rise. When an item's price starts to level off, usually the clan owner will tell everyone to sell, or dump, their item, usually causing a profit. Note that it is usually quite hard to sell the item when everybody else in the clan is trying to sell at the same time, so be wary when joining a merchanting clan.

Note: Not all merchant clans are legitimate. Some merchant clan leaders' have a certain item that they have crafted, smelted/smithed, cooked, etc., which are worth much less than what they originally bought them for. In this case they would make people buy the item at max price, raising the price, and therefore getting all, if not more, the money they originally spent.

Other
Buying Items with a difference of 1-3 but are very cheap can be a great money maker, if you buy them by the 100s. An example would be buying around 100k in Bronze Arrows for 5, and selling them for 6. It may take awhile for the trade to be completed, but it is usually worth it.