To make the most money for garage sale items, research the items to discover their market value. A general rule of thumb is to go by the one-third rule, and have the starting point of worth as a third of its original value.
Consider the geographic location and the buyers you may attract. If you are in a higher-end neighborhood, some buyers may be willing to spend more on quality items, while others are bargain hunters, and instead usually seek the best deals. Attend various garage sales in your area, and gauge the price ranges for each to get a better idea of what may work best for you.
Veteran bargain hunters normally try to bring down the cost of an item, so price items a little higher than what you think they are worth. This allows buyers to feel as though they've gotten a bargain for an item after asking for a lower price.
As the day goes on and the garage sale is nearing its end, be prepared to lower the prices. Serious buyers typically go hunting for items in the morning, so sellers experience slower sales later in the day. If you have been wanting to sell a specific item at a set price, but buyers are not interested, it becomes a matter of which is more important: selling that item for less, or not selling it at all.