There are things I'll do and things I won't do when it comes to playstyle and gear advice.
I'm not going to tell you that there's a best spec for leveling. There are many ways to level and Mists of Pandaria is all about doing what you want to do, so following what I do may not be best for you. I'll have you know that I think leveling is far too easy still, so I tend to pick the inefficient or harder ways of doing things on purpose just to keep it interesting.
I'm also not going to debate which faction first with people. The gear choices are as varied as the leveling choices, and are meant to be mixed and matched as your drop luck will do for you. I will, however, point out the reputations you'll want to at least reach for reasonable raiding preparations.