Instructions
Obtain a sport card price guide for the type of sports cards you own, or access a price guide on the Internet. As of 2010, the most prominent names for trading card pricing were Beckett and Tuff Stuff, both of which produced guides in magazines. Free online price guides for sports cards can be accessed at tuffstuff.com or portasite.com.
Examine your cards for flaws with a magnifying device such as a jeweler's loupe or a magnifying glass. Worn corners, creases and stains will drop the value of the card, as will production issues such as improperly centered card photos.
Find the card year of issue, the manufacturer, and the number of the card. Both the year and the manufacturer are located on the card's back. The card number location may vary, but is typically a one to three digit number on the card's back.
Look up your card's value in the price guide using the identifying information (year of issue, manufacturer, and number of the card.) The prices listed will range from high to low, depending on condition. If you found no flaws in the card at all, it could qualify under the high "mint" status, which the guides usually note as MT. The price listed under the MT column will be the value of the card. If the card does have flaws, check the other columns for the current price.