Solo Merchanting

Solo Merchanting is proberly the hardest form of Merchanting in the game. Its almost based 100% on luck and a great understanding of the Grand Exchange.
First of all you will want to make yourself over to the Grand Exchange Database. Search for any items you like (preferably with a low 4 hour limit). You want to find an item that has just finished a crash (or looks like its going to finish). This can take a very long time so be patient and attentive.

Once you have found the item you have decided to Merchant, log on to your account and try buying the item at minium. If it buys instantly then choose another item (it means its still crashing). Once you have found an item that doesnt buy instantly at minium try to buy it at market. If it buys instantly then spend about 50% of the money you are willing to invest on the item (you may want to spend more but it will be risky if it is your first time). Once they buy store them in your bank and do whatever you want to do in the game. If the item doesn't buy instantly choose another item.

Keep checking the Grand Exchange for updates whenever you are on the internet. If it has gone down a little on the first update dont worry because it will proberly go up the next one. After every update try selling one of your items at market price (only if it is a cheep item (-5k) if not just leave out this step) if it sells instantly keep your items and if not sell them at minimum price. Also use your common sense, if you dont think the item is going to rise any more just sell at market price.

Solo Merchanting is very risky so if you are inexperienced at merchanting I suggest you first get some more experience from the other methods.