The coal trucks are one of the best ways to gain coal. After mining a full inventory of coal, you can put your ores in the carts just to the north. After there is 120 coal in the truck, you can pick up your ore in Seers' Village at the other end of the tracks near the bank. Remember that the carts will not hold more than 120 coal. An agility level of 20 is required to get here. However you can walk around the fishing guild, (by the Moss Giants) and then walk through the gate on the western side to enter this area.