Be sure to build up your Echo Meter during each battle so that you can unleash your special attacks with more damage. You build the meter by attacking enemies with your regular attacks, which will build it up to 4 hits, 8 hits, 12 hits, 16 hits, 24 hits, and 32 hits (the latter being the highest). Unleashing special attacks at that plateau will result in the most powerful attacks your characters can use, but be sure to use them in the present battle, because the meter, even if unused, will be reset before the next battle.