The best way to make money is to play the Auction house. Get gathering professions like skinning or mining. Questing will get you a lot of wow gold, as well as running instances and selling everything you get in your gathering professions. If you want to make wow gold, you can well depend on what level you are. The outlands are great for wow gold making.

The easiest way to make wow gold is to grind for things so others don't have to. That is how it usually works. The lazy people will just buy the materials off the Auction house rather then grind it out for themselves. Your hard work will pay off. You will usually find wow gold ore inside of caves, best to go to mountainous areas like the hitherlands, arathi higlands up around that area, and just cruise around the outskirts and look for caves. For example you can farm motes at the elemental plateu. Go on your server's auction house and see what objects farmable at level 70 and see what sells the best. So go check it out, i farmed aldor signets for a while and made some nice money, but the objects that sell the most differs on each server.

Hope this was helpful. There are numerous places to farm wow gold. You have to pick the place that fits you best. You will also find a lot of iron and other things along the way. Obviously, the best area would be in Outland since it is the high level zone at the moment. I know I usually spend most of my time out in Nagrand since it has tons of gathering materials.