I used to wake up before school, dump my entire stack of gold on the GE for bones (just the regular ones) at a few gp below average price. By the end of the day the order would usually be fulfilled. Then I'd dump them back on the market at a few gp above average price and it would be fulfilled by the morning.

Most days it would net me a small profit, ocasionally prices would fall slightly throughout the day and I'd lose a little, but equally some days it would rise and I'd make extra.