I just started playing again after 3 years? maybe 2 and a half. Anyway not the point. I pretty much plan all my battles before they begin, I'm still in the phase of getting all the abilities I want on my characters so it would seem that I have a poor party set up, but with a little planning and party setup/special abilities 2 thiefs 2 summoners and a fighter class is all you need for any fight, storyline or otherwise (my current party configuration for at least 3 more battles).

I don't really grind out any extra battles so you've got to be able to level up those weaker classes and you need em set up with abilities that make um useable

My biggest tactic is picking the abilities you are always going to use, and not upgrading anything until I have them, also upgrading the ones you'll need while class switching is important. It's also nice to have characters who are weaker with the "BASIC SKILL" "accumulate" set up, so they can hide in the corner and still gain jp

(I've played the darn game so much before I have almost all of the battlefields memorized but playing to their strength is nice, IE archer to the high ground)