There are three ways to sell your coins:
Selling coins yourself can bring maximum profit because you bypass the middle-man and sell directly to paying customers. You are in control and you get all the money. However, selling coins takes skill and work, and it also involves risk. The alternatives are to consign your coins to coin auctions or sell them to coin dealers, and both these methods involve paying fees.
Before you sell your coins, you must have a general idea of what they are worth. Use this web site, other web sites, or printed coin catalogs for this purpose. Most libraries have coin catalogs.
Consignments often bring more profit than selling to a coin dealer, but you assume most of the risk. In a consignment, the coins may not sell at what you hoped for, the coins may be returned for a refund, or the transaction may turn sour in any of a dozen ways. Selling coins to a coin dealer is the easiest and fastest method, but the dealer takes all of the risk and your profit is generally lowest of the three methods.
Internet business. If you place a 'coins for sale' ad on the Internet, you become an Internet businessman. You must have computer skills such as e-mail and photo processing, and you must have good inter-personal skills to develop relationships with potential customers. People will not send money to you unless they trust you.
About Coin Auctions: The Big Time. There are about 10,000 coin dealers in the United States, and half again as many worldwide. Most dealers are small Mom and Pop coin shops serving local communities. Large international dealerships handle high-end collectibles for serious investors and collectors who easily spend $10,000 US dollars on a single coin, and often top $1 million for a significant rarity. If you have a single coin worth more than $1,000 US dollars, contact CoinQuest for a list of the Big Time dealerships. Otherwise, the best place to find reputable coin dealers is the Professional Numismatist Guild (click here). Big time dealers run national and international coin auctions, and you can usually consign coins worth more than $250 to them. Typical seller fees run between 5 and 20 percent.
eBay Consignment. eBay provides a means to consign your coins to auction while lowering risk, maintaining control, and setting prices. There is a mammoth collector following on eBay, and rare coins almost always achieve fair market value when sold on this popular web site. eBay and PayPal fees are small, about 5 percent, and they are your only expenses. As with CoinQuest ads, your computer and photography skills must be viable. Further, you must have a decent eBay feedback rating or collectors will not buy from you.
The steps involved with an eBay sale run roughly like this:
The Bad Time. Coin dealers operate without regulation. Most are honest. There are some dealers (my guess is 10 percent) who are dishonest and buy coins for much less than they are worth, or sell coins for much more than they are worth, or both. Not only that, counterfeits abound in today's market, and single coins worth more than $250 should be certified by one of the following services: PCGS, NGC, ICG, ANACS. Look on the Internet for information about these companies. Do not use other companies.
Sell to a Local Coin Shop. Take your coin to a few local coin shops (look online, in the yellow pages, and on the PNG Dealers web site) and ask the proprietors for offers to buy. Any dealer worth his or her salt can give you an appraisal on the spot after a few minutes of close inspection. If the dealer asks you "how much do you want for your coin?" or "how much did the other dealer offer?" don't answer the question. Instead request that the dealer make an offer, which he or she is perfectly capable of doing. Don't let the dealer disappear with your coin to "check it in the back room" which could be disasterous.
Sell to an Internet Dealer. There are many reputable coin dealers on the Internet, and this may be your best option if you live in a rural area without local coin shops. You can e-mail pictures of your coin to dealers who encourage you to do so, but ultimately a dealer will need to see the coin in person to make a final offer. Use the picture on CoinQuest to describe your coin initially. You need to develop a working relationship with an Internet dealer before the transaction can be a success.
Pricing. For typical, problem-free coins under $1000 USD, most coin dealers pay about one-half of retail price for coins they buy from collectors or from the general public. This markup allows the dealers to keep their businesses afloat. High-demand coins with good dates, good grade, and good eye appeal are easier to sell than most coins, so dealers often require less markup for these rarities. On the other end, coins with scratches, stains, spots, and similar damage, or coins that have been cleaned or polished, are almost impossible to sell to collectors, so coin dealers do not buy them at any price.
Coin Photography. Taking useable pictures of coin is not easy. A cell-phone camera will not do. It is wise to enlist the help of a photo-minded friend if you are not so inclined. Provide proper lighting, shut off the flash, and use macro mode. Be sure to take both front and back. Process your photos with image processing software to make them look exactly like the coin. Crop and re-size images to at least 400 x 400 pixels. Smaller images are not useful.
Shipping Coins. Talk to your postmaster first, before you package coins for shipment. Domestic US mail is incredibly safe, but shipping internationally can be a headache. Wrap your coins securely. Never put tape directly on coins.
Collections v. Accumulations. A bunch of coins gathered in a box over the years is seldom worth more than face value. If the box has gold or silver coins, they will certainly be valuable due to precious metal content. To be really valuable, coins must be collected by an industrious collector who studies the subject using various reference books.
Become a Collector. Perhaps you should not sell your coin at all! Consider becoming a coin collector, or encouraging someone else to do so. I started collecting when I was 10. Now I'm older (a lot older!) and coin collecting is still one of my favorite endeavors. It is a hobby that sticks with you. They call it the king of hobbies for good reason. Be sure to read up on coins before spending any serious money on them.