One of the leading ways that game companies catch gold sellers is by watching mailboxes. A lot of large companies have emplemented automated sophisticated automated notification systems for emailing or even calling a gamer as soon as their delivery is sent.
Due to the fact that quickly opened mail is less susceptable to detection, it appears that the detection method relies not on scanning complete logs of all mail, but an active scanning function which takes several hours to make a pass through all ingame mail accounts while flagging suspicious trades via use of programmable filters.
A common misconception is that delivering currency via ingame mail will be safer if unusual amounts are sent, such as 101 gold, and seven silver, instead of just 100 gold. Another misconception is that including a message to disguise the delivery will trick game masters that may review it. "Hey John, thanks for helping me with Math class. Hope to see you max level soon, looking forward to raiding with you."
Face to face trades are quickly replacing in game mail delivery as the most popular deliveyr method. Many trades are still detected, however. Game companies are also beginning to track face to face trades, specifically locating trades which they deem suspicious. The most effective method of avoiding such suspicion is to never trade money for nothing. Have the recipient put a worthless item into the trade window.
Beginning with Everquest II, many games now feature factions which are unable to directly trade with each other. This poses a challenge for gold famers. In most factional games, the only way to deliver between factions is to use a neutral auction house or trading portal. Same faction transactions via the use of an overpriced junk item in an auction house is not recommended because other players can notice the item and report their suspicions. It is also common for players to publically broadcast their distaste when they see something that looks overpriced. Before purchasing or selling currency to a company that brokers it, it is wise to spend a few minutes googling for customer reviews.