Keep in mind, however, that making a low-ball offer just as the sale begins won't win you any points with a seller. If you find something you really want early in the day, be prepared to pay full price or accept a pretty nominal discount.
To get the best bargains at garage sales, return late in the day. If a piece was priced very high to begin with, and sometimes garage sale antiques are these days since lots of people think their old stuff is worth a fortune, the seller may come down significantly as the sale drags on. They may very well take a lower price at that point rather drag that unwanted item back in the house or donate it to charity.
Learn how to bargain successfully in other venues: