Gwen Glass Carbone — a professional auctioneer, an eBay PowerSeller, an antiques dealer, a tag-sale pro (she attends more than 500 each year), and the author of How to Make a Fortune With Other People’s Junk (McGraw-Hill, $17, www.mcgrawhill.com) — suggests the following starting prices for popular yard-sale items. Of course, this is a general guide; a number of factors, including age, condition, and consumer supply-and-demand, can increase or decrease an item’s value. “And if you have an item that is signed or dated by an artist, maker, or manufacturer; is in great condition; is of an unusual form; may be antique; or seems particularly unique, you should do some research to find out if it’s worth a higher price,” says Carbone. Check price guides, consult an expert (such as an antiques dealer, an appraiser, an auctioneer, or an estate liquidator), or do a “Completed Listings” search on eBay to get a better understanding of the marketplace.