If you are like me and want to be the first one to set the prices for the new ores and get max income you'll want to max your gathering skills ASAP. Here's what worked the best for me:
1.Get flying License and train your professions
2.Go to Hyjal and mine obsidium till you hit 475 skill
3.Next go to Uldum
Here's a map of where I found most of the elementium veins lie:
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You also get some Rich Elementium Veins and Pyrite as bonus. And since most people are too busy leveling up you'll be relatively undisturbed.