Whenever you stop at a camp to rest there will be a box at the top of the screen that says 'Trading-Time'. If you tap 'Go!' before the timer runs out you will be able to participate in the trading mini-game with other campers. The trading mini-game allows you to offload items from your pack that you don't have use for and gives you a chance to make money off those items. The mini-game also enables you to purchase items of other players who will also be putting the items they no longer want on the the conveyor belt.
During Trading-Time, items are placed on the conveyor belt where they will slowly move down the line. The key to winning Trading-Time is the placement of your items. Place your rarer, higher quality items near the left as they are sought after items that are likely to sell and place your common items near the middle. Knowing what types of items sell and which don't takes experience.
If an item is unpurchased it will go into the wood chipper and you will be given less money than if it was sold. If you place an item on the conveyor belt by mistake you can simply drag it back into your pack without being penalised.
The Conveyor Belt
Left Side = Higher Price
Right Side = Lower Price
Orange Price Tags = Yours
Red, Blue, and Green Price Tags = Owned by other Traders, items that you can buy.
Rounds
There are four different rounds for trading, each one of which focuses on the professions. To maximise your financial gains it is important that you only sell items during the appropriate rounds. For example, if you try and sell tools during the food trading round you will get less than half of the items value.
Multipliers
To make the most amount of money during Trading-Time you need to invest on multipliers for your items to increase their length of time in the rounds. The more time you have in each round of trading means you have more opportunity for your items to sell for a decent price.
Green Tagged Items
Item that don't sell during the appropriate round will be green tagged and drop to 50% or less of its value which makes it an opportunity if you have space in your pack to grab some inventory for the next campsite.
Unsold Items
Make sure you do not leave your unsold tools on the conveyor belt during a round change, if the round is about to change you can pick up your items without being penalised. The only time they should be left on the conveyor belt is at the end of the game where they will be destroyed for the value on their tag.