Buying and selling gold is a surprisingly straight forward process. The spot price of gold is set by world financial markets and is revealed to everyone when it updates every day. You can expect to get a little less than the spot price of gold when you sell and pay a little more than the spot price of gold when you sell. Those prices skew a little higher with gold coins because of the cost of minting them.
Determine what kind of gold you want to buy and sell. Gold coins were minted as money. They have value both for their gold content and their appeal to collectors. Since most countries stopped making gold coins in the 1930s, gold coins are somewhat scarce and command values high above the spot price of gold. Gold bullion is gold cast into rounds or bars for trade based solely on their gold content. Some gold bullion looks like coins but they are not considered real money. You can also buy and sell gold in nuggets, jewelry, and gold scrap.
Determine the purity of the gold you wish to buy and sell. Gold coins and most gold bullion are .916 pure. Some gold bullion is as pure as .999. Gold nuggets, jewelry, and scrap will only be partially gold. Look for the karat value. Most jewelry is 10K, 14K or 18K gold. Look for these numbers stamped near the clasp. Assume that most nuggets and gold scrap are 10K gold.
Calculate the purity of the gold you want to buy and sell. This is easy with gold bullion. One ounce of gold bullion contains one ounce of gold regardless of whatever other metals are mixed in. Most gold coins have are 96.75% pure. 22K gold is 91.7%, 18K is 75%, 14K is 58.3%, and 10K is 41.7%.
Weigh the gold you want to buy or sell. You will need a sensitive scale that can detect fractions of an ounce. A jewelry scale, coin scale, or postage scale will work. Weigh the gold that has the same purity together. Different karat gold should not be mixed when weighing. Record the weight in troy ounces. To convert from grams, divide by 28.35. To convert from pennyweight, divide by 18.23.
Multiply the weight of the gold you wish to buy and sell by the purity. This will determine the actual gold content. For example, one ounce of 18K gold contains .75 ounces of pure gold.
Find the spot price of gold. This can be found on any financial market website. A link to one if provided below in the Resources section. Keep in mind that the spot price of gold changes every day.
Multiply the spot price of gold by the actual gold content of what you are trying to buy or sell. This will determine the actual value of the gold. This figure is the starting point of all gold transactions.
Negotiate with gold buyers and sellers. In general, prices are determined by the spot price of gold. Expect to buy and sell gold bullion within 5% above or below the spot price of gold. Gold scrap will buy and sell for about 5% less. Gold coins can be valued considerably more depending on their rarity and condition. All prices are negotiable, especially if you are dealing in large quantities of gold.