As topic says, WoW Insider has released three guides to each of the dungeons in 4.3, it's worth a nose!
End Time
Tankspot video guide
Well Of Eternity
Tankspot video guide
Hour of Twilight
Tankspot video guide
Also note that in terms of story, the three instances are chronological (in the order I've posted above). I don't know for certain, but they might follow directly on from each other as the three ICC instances did at the end of WotLK, so when you make your group of guildies, it'll be worth starting with End Time and following them through if you can.
Edit: There's a questline you need to follow to open up all the new instances (like the ICC ones).
Cog