Final Fantasy X Tips

Build Overdrive Easily
Get in a battle with a magic urn, which can be found in the Cavern of the Stolen Fayth, near Mt. Gagazet. This enemy won't attack you as long as you don't attack it, so you can heal if set to healer, cast Nul Spells and then the corresponding spell if set to rook, or have two party members escape and the last defend if set to loner.

This way you can build up Overdrive more easily ready for hard fights or if trying to abuse Overdrive>AP.