Money making guide/Grand Exchange Merchanting

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.

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

Long-term Merchanting
The following items are currently rising up slowly:
 * Sapphire
 * Amulet of defence
 * Amulet of strength
 * Amulet of power

The following items are usually stable, but may skyrocket once a month due to merchanting clans and double in their price. Beware, it may immediately drop the day after.
 * Druidic mage hood
 * Druidic mage top
 * Druidic mage bottom
 * Air talisman

Buy Low, Sell High
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.
 * Warning! Buying and selling in large quantities can cause pressure in the Grand Exchange market and contribute to market crashes!
 * 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 to 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 weary when joining a merchanting clan.