For starters, the addon I used is Auctionator.
I also use the general principle of using Auctionator's "AH" button to see if an item is profitable. While that may be an over-arching idea, the tough part is finding trade goods / items which people are willing to buy. One that I've found in recent days is Blacksmithing Rods.
I am on a Blacksmith who only has skill level 409, however, and this limited me to only 5 Rods trained. That being said, out of the 5 Rods, 3 of them had very high profit margins..
The three Rods I created and the Cost:Value ratios are as follows:
- Fel Iron Rod (44g88s96c:120g - Profit: 75g11s04c)
- Truesilver Rod (4g28s80c:54g - Profit: 40g71s20c)
- Golden Rod (73s85c - Profit: 25g26s74c) Profit: 91g17s37c
Total Cost:Value ratio: 49g91s61c:141g8s98c - Profit: 91g17s37c
As you can see, the profit margins are very visible in these transactions. As it might be said in today's economy, it's "paying pennies on the dollar". I do have to put a disclaimer in here, however. This is not a market to attack in order to gain instant profit. While the demand is low, the supply is, too - which means it doesn't require much upkeep dominate the market. If you create them and leave them, they will most-likely either sell or expire - not get undercut. There simply isn't enough supply to result in much competition. It may take you a few days to sell a given Rod, but the mark-ups are pretty incredible in this Market so I strongly suggest you at least give it a try!
I hope this write-up has helped to add clarification; and, as always, good luck!