adopt what I do when I trade once a year:
1. If trader needs to "empty inventory" AFTER you saw the item, raise Caution to Level 2.
2. In the last part, where you both his the green mark, first go over ALL the items again.
3. In the above part, if the item is Unidentified and the trader needs to do something in Inventory that causes him to cancel the trade window, then retrade again, LEAVE THE GAME. Only stay if its an item like an Unidentified Windforce and you're trading LOTS for it. Even then, tell the trader to clear his inventory before looking at the item.