Make sure you have Weak. It can be very easy to assume that FuSoYa will have Weak, and you're going to be sad if you're in the Giant and find out he's not there quite yet
Put the Weak caster in the center slot
if Tellah, and you save some speedy people, give him +agi gear, or maybe have a Hermes handy
Know how many d machines you need. Think about target spells/levels for characters. Nuke/White are common targets.
If someone is close to slingshot range, think about setting it up
Have the consumables (ethers, cure pots, life pots) to meet your exp goal
Give as many high HP people fire resistance as you can (Cecil, Cid are big targets for this, since any part of dragoon/ice defensive gear provides it)
It's better to over-prepare than under-prepare
A SomaDrop on Tellah or Fu will give them an extra weak cast at full mp.