To create a TRADING POST place down a sign and in the respective lines:
Example:JTPROG selling a stack of 64 dirt for $4 a piece
line1... [trade] line2... $4.0 <--This $4 is the price per amount of units (defined below as '1'). If a '2' was defined below 2 dirt would cost $4. line3... 1:dirt:64 <--The '1' also means the buyer buys 1 dirt per click. '64' is amount you want to sell, taken from yout inventory. line4... JTPROG
NOTE: The formatting must be EXACT. so in line2 a dollar sign and 1 decimal place is needed. Follow the example carefully. MORE DETAILED EXPLANATION BY VIOLETRIOT:
If you created your sign correctly, the [trade] will turn blue.
I've already used the trading posts quite extensively, so I thought I'd add in a couple of points JTPROG left out that might prove helpful.
Trading posts, as indicated above, are set up by placing signs. They allow players to sell items while elsewhere in the world, while AFK or even while offline. The requirements for trading posts are quite few. In fact, there's only one. The item you are intending to sell to the general public, MUST be located in your inventory or backpack before you set up the trading post. It cannot be stored away in a chest at your home or anywhere else. This brings us to the next point, how these trading posts operate. When a trading post is properly placed, the appropriate item will be taken from your inventory and temporarily stored "inside" the sign, awaiting potential buyers. Therefore, do not be alarmed when the item you are intending to sell disappears from your inventory.
As indicated above, there are four required lines on the trading post sign.
Line 1: [trade] Line 2: Price Line 3: Unit:Item:Total Stock Available Line 4: Seller
The following will use JTPROG's example. Line 1: [trade] Line 2: $4.0 Line 3: 1:dirt:64 Line 4: JTPROG
Line 1 is necessary and unchangable, indicating that the sign is in fact a trading post.
Line 2 is the price you are setting for the item. One detail regarding this line should be highlighted. When the trading post sign is properly set up, there should be a slight difference in the second line. In the above case, $4.0 will turn into $4.0:$0.0 The first value indicates the price you are selling the item for. The second, new value, which always starts at $0.0, is the total amount of revenue generated from sales. In other words, it is the amount of money you have gained from customers.
Line 3 has three values, all of which must be entered properly for the trading post to work. The first value indicates the amount of said item you are selling per transaction. Using the above example, 1 of each item will be worth $4.0 The second value is the name of the item itself. Many items have considerably long names and do not fit into a single line. This is when item data values come in handy. Each item's corresponding data value, for example, dirt being 3, may be used in place of names. However, when this is done, please remember to set up an additional sign next to the trading post, indicating the actual name of the product you are selling for convenience. The last value in the third line is the total amount of item(s) you have available to sell. The above example states that you have a full stack of 64 dirt to sell.
Line 4 is quite simply, the name of the seller.
When you are satisfied with the trading post, or if you want your items back and want to take them off of the market, simply break the trading post sign. All remaining stock (unsold items) will be given back to you. Note that all items, regardless of originally being able to be stacked or not, will be stacked when returned to you. However, items such as mushroom stew, despite being stacked, act as only one single unit, so be wary when using them, as a stack of mushroom stew may be destroyed after one use.
To conclude, one more example will be provided below with a short description of the general intention of the trading post.
[trade] $10.0:$60.0 1:86:58 violetriot
One pumpkin (data value 86) is sold for $10. 6 pumpkins have been sold for a total of $60.0 (6 x $10.0 = $60.0) Out of the original stock, 58 pumpkins remain available for sale. violetriot is the seller.