The best resources for making gold are not a very well kept secret. These sites and utilities are used by most serious auctioneers, and anyone looking to start making gold, even if only casually, would do well to learn how to use these.
The Undermine Journal
The Undermine Journal is first on my list. It is a site that does a lot of things, but most importantly, it shows you the price for any item on any realm. You can look back at how the price and supply for sale changed over the last two weeks, and you can see all the auctions of any competitor by clicking on their name. You can also compare prices on your realm to prices on other realms or the other faction on your realm.
The potential for research here is limitless. Any time you're looking for a new market, the first question you have to ask is whether there's enough of a gap between cost and price to support your margins, and seeing the answer to this question over a period of time is way more valuable than seeing just what's on the Auction House when you decide to check into it.