Final Fantasy II: Unarmed is broken and works where actual weapons don't. If you are having trouble with an enemy with high physical defense but you have no good magic, just punch them.

Final Fantasy VII: Visit Gungaga, a tiny town right after you get the Buggy but before Cosmo Canyon. Explore all the houses and have Tifa and/or Aerith in your party.
Explore all the houses in Icicle, the snow town.
Go back to Nibelheim Mansion basement on Disk 3.

Final Fantasy VIII: Draw Siren from Dollet Tower boss
Learn L-Mag RF
Turn Tents into Curaga
Junction Curaga to HP
Congratulations, you're not invincible, even before leaving for Timber.


Final Fantasy XIII: Always have a SAB in your party if possible. It will make your life so much easier.