To price used furniture, you could visit some used furniture stores or flea markets in your area. Check prices for similar furniture. Checking prices could give you an idea on prices. Look here for more information: www.stretcher.com/stories/03/03jul07d.cfm
In order to set a fair price for your used furniture first visit some second hand stores to see what the going price is for used furniture. Then take into consideration the quality and condition of your piece.