Photo: Burcu Avsar

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Rule #2: But First, Know What It's Worth
In 2007, a ceramic bowl sold for $3 at a tag sale in New York state. The bowl's new owners then discovered it was a 1,000-year-old relic from China's Northern Song Dynasty; it was snapped up at auction for more than $2 million. Here's how to determine whether that gilded birdcage bequeathed to you by Uncle Sal has hidden value—before you part with it.

Google and Ebay: If an item has no identifying mark, search descriptive words (for example, "green glazed pitcher, grapes on side") to find images or websites that could provide key information. Or browse through eBay's Collectibles & Art section for similar items to determine current market value. If you know the name, designer, or manufacturer of your collectible—and if it's worth something—there's a good chance you'll find an identical or similar one here. Curious about whether your yellowing copy of To Kill a Mockingbird has any value? Type in the title, author and date of publication, and this site will search thousands of booksellers to find any offering the same or a similar edition.
Naomi Barr