FreeLancer, you can edit previous posts to add to them to bypass the character limit.

MNK - Keep all stacks of your effects up. Greased Lightning, Twin Snakes, Dragon Kick, Demolish, Touch of Death (until TP becomes an issue). Highest sustained 1v1 dps.
BLM - Never stop casting if possible. Maximize Astral Fire time and use, as well as proc use. Highest single attack damage in critical hit Fire III's, as far as I know.
DRG - Time your bursts, mow down things hard with them if you do it right. Most lethal burst damage.
NIN - Don't waste a Ninjutsu window, be ready to use utilities (especially Goad) at any time. Most overall helpful dps-based utility.
BRD - <Blunt Arrow> <Just used it.>, never assume the DPS you lose with a song is more important than the utility it grants. In Ballad / Paeon's cases, learn how much is enough to avoid too much, as that CAN be a loss. Incredibly good burst dps with cooldowns.
SMN - Look up three posts.