Any achievement (or reputation) geeks out there?

I was wondering what the most efficient way to farm rep was, I intend to get all the factions to exalted bar the insanity grind thingy ones.

But like just standard cata/mop/faction/wotlk/tbc ones and a few of the easier vanilla ones.

But I get kind of lost and confused whenever I wanna farm rep, I don't really know the most efficient way to do it.