Breaking up with Azeroth is hard to do, especially if you're a miner.
Cognizant of the fact that faster XP gains from old-world questing would give me fewer chances to skill up, I leveled Hooloovoo as a mining fiend, cutting down whole swaths of mobs just to be able to set my pick against one more mithril vein. I was diligent from day one, super diligent even, but to little avail: I still hit level 58 with only 267 mining skill.
Now, for those of you who don't spend your days deep within the bowels of the earth hunting precious gems and minerals, here's a quick primer on leveling mining so that you can mine in Outlands. Once you outlevel mithril (the nodes will go green at 225 and gray at 275), the majority of your skill points will come from dark iron and truesilver deposits (which require 230 mining and go yellow at 255 skill), and after that, from thorium. You can start mining thorium ore at 245 skill (the small veins will turn yellow at 270), but you can't mine rich thorium veins until you reach 275.
Now, the reason I'm bothering with all the numbers has to do with one simple yet aggravating fact: you cannot mine anything in Outlands until you have 300 mining skill. This generally means that after hitting 58, you're going to spend at least an hour or two running around in circles grinding up your mining skill.
My choice of location for eking out those last 30-40 points is the Burning Steppes, and here's why. First off, it's a very short flight from Stormwind, so it's easy for me to hop a portal in Shattrath and head out there. Second, all the mithril nodes in BS have a chance of spawning truesilver or dark iron, both of which stay yellow for longer as you're leveling. Finally, it's very easy to get around: there are almost no elite mobs to deal with, the terrain is conducive to making nice easy circles around the zone, and these days (as everyone besides miners leaves Azeroth at 58) it's pretty empty, so there's little ganking or competition to worry about. It took me about an hour and forty-five minutes to level my mining from 267 to 295 skill.
At 295 I was able to pack my stuff and hearth out thanks to [Enchant Gloves: Advanced Mining]. I highly recommend this enchant: buy yourself a pair of trash or white gloves and spend the three vision dust and truesilver, and enjoy the bonus 5 points to your mining skill. If you also happen to be a goblin engineer, you can really save yourself some time by wearing both the glove enchant and your trusty [Goblin Mining Helmet]. If you keep these on you throughout the leveling process, you should be able to mine nodes that are usually inaccessible to people at the "normal" level for a given zone (like the thorium veins in Un'goro), which means not only will you get to head to Outlands at a lower skill level, but you'll also reach that skill level faster than someone without the helmet/enchant.
And that's all the advice I have to share on mining. If you've got a good tip or a favorite spot for leveling mining skill, leave me a note in the comments. And for all you budding miners out there: good luck, godspeed, and above all... don't delve too deep.