Druid must be balance and preferably be flexible playing Restoration, although I doubt you will be called on to do this. Hunter, I have no idea. Just don't be retarded and play the spec that does the most damage lol. Mage same thing, although I have more confidence in Mages not being retarded over say a Hunter.
Show up with your own consumables please! MoP massively sucks with raid preparation things like Cataclysm did, so just bring your own stuff. Feasts are magically provided randomly from random people so don't expect them to be down all the time!
We raid 7-11 (pacific), Sunday-Wednesday. Starting early is completely OPTIONAL and depends on whether people are randomly around and/or don't have anything better to do. We rarely go over our allotted time by any significant amount outside of a trivial amount of minutes. As long as you can 95% of the time make the scheduled dates, you're in the clear.
Although it happens super rarely we have had raid days on non scheduled days this expansion. They are usually at the expense of a regular raid day and happen on a Thursday/Friday. DISCLAIMER! These aren't mandatory and nobody is expected to actually show up for these. In the 3-4 times we have scheduled these this expansion they are about 50/50 on actually happening, so don't feel bad if you could never make them.
Random stuff does pop up so we don't expect 100% attendance. Just please for the love of god give notice though!
Think that's about it.