Be sure to have updated bossmods.

Bring flasks, have enough to last the entire raid.
Bring class consumeables, for all your speccs.
Bring potions, health, mana, rage, whatever works for you.
Bring food. There will probably be fish feasts, but always have your own food as well.
Bring scrolls. We might not have that buff you need. Check AH or with a scribe and see what scrolls you can get.
Bring gold. The repair vendor have a large family to feed.
Be on time, or you will loose you spot!
Always prepear to have fun and smile :D