Buy low, sell high.

The simplest way of making money, buy low, and sell high. You have to exploit the laws of supply and demand. With my main account, I often put a buy offer on the grand exchange for yew logs at around 5 gp lower than the market price. Once I have bought a large sum (10,000+) I will sell them for the market price. This strategy is for making trades within a relatively short period. The gains are small, but by making many of these trades, they add up. I will often have a buy and sell offer up at the same time. This way I am feeding the buyers who are willing to pay more while at the same time making other sellers wait. And they often will put their sell offer lower in order to expedite the selling process.