[TheSlyMoogle]

Actually if you just fight every random battle that you come across you'll be able to max your innate job classes by the time you get to the last boss. Yes I did grind to max level in the 3 innates before my last battle. That was really stupid of me because I spent all of the last "dungeon" really wondering around without much of a purpose.

Like DM said, just fight every encounter (With the exclusion of chapter 11 and you'll see why lol), and you'll be alright.