A garage sale takes work, from figuring out the right prices to setting up enticing displays. By Leah Dobkin, Contributing Writer August 1, 2009 EDITOR'S NOTE: This article was originally published in the June 2009 issue of Kiplinger's Retirement Report. To subscribe, click here.Conducting a garage sale is a great way to make some extra money in this sagging economy. I decided to hold a garage sale a year ago after I had bought a duplex for investment purposes. It contained the possessions of the original owner, who was born in 1890, as well as those of his parents and his daughter. Before I opened shop at my home in Milwaukee, I solicited advice from Donn Moczynaski and Brian Belli, who conduct estate sales and own an antique mall. Sponsored Content If you're going to hold a garage sale, you'll need to decide if there's anything you can sell online. You could make extra money on collectibles. I sold Harley Davidson knickknacks on eBay because there is a hot market for them. I also aimed for online collectors to sell a German doll from the 1880s. Because I included the contents of three generations, my garage sale was bigger than most. The garage sale lasted two weekends, and more than 400 people stopped by. Advertisement I displayed about 300 items, including dishware, clothes, toys, furniture and records. Old postcards, maps, magazines and photos sold quickly. I sold unusual items, such as an old sauerkraut barrel and an American flag with 48 stars. While setting prices, conduct some research on very old and unusual items. "The time you invest researching will pay you back tenfold," Belli says. There are diamonds in the dust, and you want to get a fair price. If you think you may have some old pieces of value, read Eric Knowles Antiques: A Beginner's Guide With Over 1,400 Illustrations (Mitchell Beazley, $30). Also check consignment shops, eBay, Craigslist and Google to determine market value. I sought appraisals for my German doll, an embroidered handmade cloth, and some old records and books. An original receipt or box will increase an item's value. Know your bottom line, and then negotiate. You should mark items slightly higher than what you expect to sell them for. Also check local ordinances, which could regulate the number and size of signs you can post. I wasn't allowed to conduct the sale on my front yard, so I used the garage and backyard. You can buy signs and price stickers and find tips for sellers and buyers at www.yardsaleportal.com. Advertisement Keep items accessible so that buyers do not have to rummage through boxes. Also, be creative. Kathy Peterson, host of "The Balancing Act" on Lifetime Television, says it's important to have colorful displays. "Create beautiful vignettes using decorative home-decor items, like pottery and boxes, and group them in a theme," she says. "If people love it all, they'll buy it all." Barry Izsak, author of Organize Your Garage in No Time (Que, $17), says curb appeal is key. "Use lace tablecloths, twinkling lights, balloons and scented candles," says Izsak, a professional organizer in Austin, Tex. I had a large, hand-carved, wood fireplace mantel with its original receipt front and center. I displayed decorative pottery and embroidery on the furniture I was selling. And I played upbeat nostalgic music from the various eras represented at the sale. Look Out for Pros and Thieves Advertisement Watch out for antiques professionals, who will try to lowball you and then sell your items at much higher amounts. They'll look on the bottom of items for markings, and they may come with a magnifying glass or a jeweler's loupe. When some pros who read my ad came by my house days before the sale, I told them to return during the sale. Also be aware of thieves. Belli suggests keeping small valuable items in a locked display case and larger valuable items close to you. Recruit friends and family members to watch your stuff. Often fraudsters will collect a bunch of items and hide an expensive item in the middle of the pile. Look over what people want to buy. Check furniture drawers for unpaid merchandise. "Just be vigilant, and have fun," Belli says. My garage sale was a blast -- and my wallet was $4,000 thicker. For more authoritative guidance on retirement investing, slashing taxes and getting the best health care, click here for a FREE sample issue of Kiplinger's Retirement Report.