It really depends on the character...

For Terra, I'm trying to teach myself to resist using her EX-Burst cause I can easily do far greater damage by spamming her dual casting spells. Give her Exp converts to EX Gauge and you can almost keep her in EX-Mode permanently by spamming Meltdown, Flood or the Holy/Flare/Ultima combo.

The last combo becomes incredibly difficult to dodge in EX-Mode and since she does such high brave damage she can quickly raise her Brave even if the enemy is Brave breaked.

My other favorites like Squall and Gabranth are much more tricky to use. I'm also trying to learn how to use Kefka which is becoming more and more about relying on a certain move to set up every other attack he has.