Instructions
Check the Yellow Pages under the heading "Coin Dealers and Supplies" for a list of your local coin stores. Alternatively, go to the American Numismatic Association's (A.N.A.) website for a directory of affiliated dealers. While stressing that the dealers it lists are unaffiliated with the government, the U.S. Mint also offers a limited database.
Go to a coin show. Held all over the country and often lasting several days, these meets are an opportunity to meet coin dealers face to face and, after browsing the cream of their collections, to buy at a discount. The website 2-Clicks Coins has a regularly updated list of coin shows.
Browse online auction sites, where many of the lots are in fact offered by dealers. Usually there will be a link to the dealer's online shop, or you can send him a message if you'd like to quiz him on something.
Type "coin dealer" into your search engine for a list of nationwide dealers. Narrow it down by specifying a region or a type of coin (mint, bullion, commemorative, proof and so on.)