Well, on my main character people always ask me, "How do you have an epic flying mount, and so much gold leftover still!?"
(yes, i'm serious... it's quite annoying)
So I figured i'd share it with you guys here.
What I do, is the very commonly known "Play" to the auction house routine.
I target Designs, and formulas that are unerpriced. (Jewel crafting/enchanting)
First off..... You must now make BEST friends with wow.allakhazam.com.
Search the item(s) you find, and go to the Pricing options listed.
They will have a High price, a medium price, a average price, a low price, and a "Most Common" price.
Generally I'll find "Glowing Nightseye, Balanced Nightseye, Bold Living Ruby, Dawnstone, etc. etc. etc." designs, and they will either be under 200 gold,
or I will message the seller, and bargain him down under 200 gold.
At this point I go back to allakhazam, and search whichever i've found, and i'll start auctioning it at it's "Most Common" price, which is generally more than the average, yet lower than the (ridiculously too high) high price.
And within maybe a weeks worth of rummaging through all of this mumbo jumbo, i'll have about 2,500 gold.
I guess it really may depend on your server, if that's so - I must get lucky, been doing this for about four years on world of warcraft with all of the past trade goods, and truly ALWAYS made a lot of a profit.
(Example: Design: Balanced Nightseye is my best seller, just simply using these prices)