One of the biggest mistakes people make when holding a garage sale is not advertising enough. Most people think that it is enough to put a single ad in the local paper one week before the sale. Usually these people are too worried that they will lose money on their sale because the ad costs too much. That is nonsense.
When you don't advertise much, you don't get many customers. When you don't get many customers, you have to sell at their price, because if you don't, there...