Aion Gold

You can sell them items for a fixed - and usually low - amount of Kinah. Some items are worth much more than a vendor will pay for it, but because this is a very simple and fast way to get rid of items you don't need, a lot of players sell items for a very low price to vendors, unaware that they could have gotten a better bargain by selling the item to another player. A prime example of this would be manastones: basic low level manastones sell for only two Kinah to a vendor, while they are worth several hundred or thousand Kinah on the market. So the only stuff you want to sell to vendors are soulbound items that you cannot trade with other players, or grey quality items that are basically junk and can be disposed of quickly by the handy "sell all misc" button at every vendor.

Most other items you will find are useful to another player in some way and should be sold via direct trade (using the ingame trade channel and whispers to find a trade partner), a private shop or the trade brokers. A private shop can be set up anywhere in the world and allows you to put up some items from your inventory for a fixed price. You can also choose a message to display in a chat bubble to advertise your goods. Of course, a private shop is only useful if placed in a location where a lot of players come by, and one of their best uses is probably to provide a specific quest item right next to the corresponding quest NPC. The big disadvantage of this trade method is that you can't do anything else while you have your private shop active, besides using the chat, so unless you are going away from keyboard for a while, you might prefer to use the trade broker instead.