Also, one bidder can try to buy more than one item. All winning bidders pay the lowest successful bid amount. This is different from a Yankee auction, in which each winning bidder pays his or her exact high bid. After the auction closes, you should contact the high bidder and arrange for payment and delivery of the merchandise. The auction will close without a sale.
Most auction sites offer an automatic relisting service, which is often free the first time.
It's up to you. You are not obligated to sell the item to the highest bidder, but it's not uncommon for sellers to contact bidders and try to work out a deal. Some services charge fees if your reserve price is not met. This information is usually listed in a site's terms of service agreement.