By the time you read this, Mists of Pandaria should be out and playable in Europe (coming soon to the US), and there's probably even a few of you who will have hit level 86 or 87. With the new talent and specialization system, I expect figuring out how to level will be easier than ever, if only because it's a lot more difficult to go wrong. Still, there's a few recommendations to make that may help you hit level 90 just a bit faster, and we'll go ahead and dispense some of that advice today. Note that all advice here is for leveling only, and may not apply to end game dungeon running or raiding.
Choosing your leveling spec
I would recommend you choose either two-handed frost or blood as your leveling spec. Blood is strong enough and has enough self-healing and emergency defense tools that will probably never die. That said, your DPS won't be as high as you might like. Frost will allow you to kill things faster but still gives you some decent survivability options in the form of Death Strike and, if you talent in to it, the Lichborne heal trick. If you do level as blood, make sure you are either queuing for dungeons as a tank, or have a secondary frost or unholy spec ready to switch to when you DPS a dungeon. Blood is still not great DPS, and your dungeon group will need better than what you can put out as blood.