You can't really, or well you can, if you have the patience of a stone that is.
I've tried a dozen or some high in demand items. What I do is check the buy orders.
Let's say copper. Copper might sell at 23 a piece but can be ordered for around 18 a piece.
You will see a couple of 20's and 19's too, but I generally go with what the lowest priced high supplier is. Which in this case was 18 copper a piece. So I thought hey, I wanna make alot of cash, why not buy a 1000? Wrong! You can't. You'd have to buy 4 stacks of 250 and sell those seperately aswell, all the while the prices rise and drop and you are stuck having an order in the TP for 1-2 hours when the lowballers finally clear the field. Let's say this doesn't happen and it does sell. Yay! You just made profit. About 2 silver worth of profit. It took you about 5 minutes to do so at that rate you'll be making 24 silver/hour. Which is totally pathetic.
Not to mention you spend more time on the TP than actually playing the game.
But mister, why don't you buy items that sell for more than copper? I did, here is the problem. For a number of fine crafting mats, the difference between orders and sales is about 2-8 copper. Resulting in about the same net profit as with copper. Copper is alot let risky though. Another problem is, the fine crafting mats selling around 1-2 silver are usually in much lesser demand. Meaning if some random comes in and decides to put up 200-300 2 copper more expensive than you, it might take many hours before those orders are filled. And then yous till have to sell them too! Sometimes, the higher the crafting mat, the items don't even sell at all. You have to wait like a day.
There are certain crafting mats that have a nice 30 copper spread difference however those are often the items that sell the slowest.
So how the hell do you guys make your money so fast. I hear people in Lion's Arch constantly saying how they make 15g/day or how they have 50+g in their bank. And this is actually people that don't buy gems, as they have much much more gold. I've spent hours scouring the TP to find niche markets that have a good balance of high demand and a high enough profit for me to try and net 1g/hour. Maybe I'm blind, but I can't find it.
Edited by Verificus, 09 September 2012 - 01:25 PM.