Are you looking for methods and tips to make decent gold in WoW? In that case, maybe the Cataclysm gold secrets that I'm going to share here will help.
1. Old raid instances like Molten Core hide many expensive items and recipes. Since the level cap has moved to 85, a level 60 raid instance like Blackwing Lair or Molten Core can easily be soloed even by a DPS class. Even if you don't clear all the bosses you can surely kill quite a few and have a decent chance to get valuable BoE loot.
2. Although the days of the Burning Crusade are long gone, some of the crafts introduced with this patch sell for fat prices. A good example that I can give you here is Primal Might. If you have an alchemist transmuter, you can make nice gold with this product.
3. Frostweave Cloth, which used to be pretty cheap in WotLK, sells now for pretty high prices because not many players farm it anymore. Since tailors need loads of this stuff to skill up this profession, it's a class of items always on high demand.
4. Another one of the Cataclysm gold secrets that I want to mention here is that with patch 4.1.0, the Formula: Enchant Weapon - Crusader was reintroduced in the game. So, if you used to farm it for gold before 4.0.1, you can once more have a shot at it.
5. I know that not many players like fishing in World of Warcraft because it's boring, but did you know what valuable stuff you can get from the Sealed Crates fished in Tol Barad? Basically you can get any resource introduced in Cataclysm, plus in Tol Barad you will also find plenty of Fathom Eel schools which are also quite valuable.
6. If you have a tank or healer, the roles that not many players choose because they require a lot of responsibility, by joining random Zandalari instances you will get a Satchel of Exotic Mysteries, which can contain plenty of valuable and also cool stuff. Among the super expensive items that can be found in this satchel you can get the Tiny Crimson Whelpling or Mulgore Hatchling.
7. The last and the most important of the Cataclysm gold secrets that I want to share here regards the Auction House. If you're not aware of this by now, AH trading is the most profitable method to make gold. If you know exactly what to buy to resell, you'll always have a positive cash-flow.
However, AH trading has certain risks. Investing in the wrong stuff may cost you. But those risks can be diminished considerably is you work with a helper.
For example, I've been working with a World of Warcraft gold guide. This way, not only that I never lost an investment, I also learned many other Cataclysm gold secrets which have brought me plenty of gold.