Trading allows players to exchange items or zulie to one another privately. To trade another player, select their character then use the 'Trade' skill found in your Skill window. Use the shortcut ALT + S, or use the menu.
Almost all items can be traded to other players. Generally, Event and Mall items cannot be traded.
Select an item you wish to trade by dragging it's icon into the top half of the trade window. If you try to trade a stackable item, it will first ask you for the amount of that item you wish to trade.
Zulie can be traded to the other player by clicking on the zulie symbol in your inventory.
To complete the trade, click 'Confirm' then 'Exchange'.