Instructions
Learn the composition of the coin. Some coins' value depends greatly on the metals that make up their composition. Prime examples are the golden eagle coins of various denominations struck by the U.S. Mint between 1796 and 1933. Many of these coins featured a composition of at least 90 percent gold. With the price of gold moving above $1,000 an ounce in 2010, that makes these coins quite valuable based simply on the amount of gold in them.
Grade the coin. The grade of a coin may range from poor grades, such as about good (AG-3), to high grades such as uncirculated (MS-63). A coin can be uncirculated if it features no wear and few contact marks. The original mint luster should also generally be present. Coins that grade in the about good range will often have so much wear that most features are barely distinguishable. Price guides can give you a good idea of how values differ based on grades.
Look for design flaws. Some coins were misstruck at the U.S. Mint, resulting in variations that can fetch high premiums on the open market. The 1955 Lincoln penny is a prime example. Some copies feature a double-die error on the front, meaning the date "1955" was stamped on it twice. Copies in very fine condition (VF-20) can fetch more than $1,000 as of 2010.
Figure out if the coin is scarce. Over the years some copies of particular coins are harder to find from some U.S. Mint locations than others. The 1854 Liberty seated quarter is one example. The New Orleans mint only produced about 175,000 copies of the coin while the Philadelphia mint produced nearly 3 million. The New Orleans version often sells for three or four times the price of the Philadelphia version in the same condition.