* You don't have to wait for a portal, summon, or level 74 to get to Dalaran. Battle ports* work just fine, but you do have to get connecting flight points to make it useful.
* If you wait until 74 to go to Dalaran, don't run there to get the flight point. There is a quest that takes you there. If you do run to the Crystal Song Forest to get there you, will find yourself looking forlornly at a teleportation device that is no help to you at all.
* On the subject of teleportation, If you're Horde, you should really save the Goblin Transponder that you use to port from Booty Bay to Gnomeregan. It can help for raiding Ironforge.
* Beware of the Animal Blood debuff in Borean Tundra. You will be killed on sight if you go into the D.E.H.T.A. Encampment if you have that debuff. It took me two deaths to figure out why I couldn't turn my quests in.
* I'm relatively new to tanking, until about a month ago I clicked to set my marks. I had no idea that you can hotkey your lucky charms.
I'm sure there are still many nuances of the game I still don't know. Share your wisdom, what's something you wish you'd been told?