Instructions
Grade your coins to the best of your ability. It's important before selling to determine a fair estimate of the grade, and therefore value, of your coins. If you take your coins to a dealer, he will determine the grade, but if you are selling in an online auction you need to estimate the grade yourself. Grades range from About Good (AG-3) to Perfect Uncirculated (MS-70). Use a guide such as Whitman's Red Book to help you determine the proper grades for each coin.
Sell your coins to a local dealer. You will usually get less money from a dealer because he has to make money reselling the coins, but you can turn your coins into cash quickly this way.
Use an auction website such as eBay. This method will get the most eyeballs on your coins with the millions of users of the site, but you can encounter a supply-and-demand issue. If yours is a relatively common coin, say a 1937 Mercury dime, then there may already be several like it listed. You are likely to get higher prices for your coins if they are rare or unusual selections.
Find an auction house if you have rare coins. If you are trying to sell some 17th-century colonial silver coins, you would be better off seeking professional help to better market your potential four-figure items. Professional auctioneers will help you get the maximum value out of your unique coins.