For Alliance, head to the northernmost dock at Stormwind Harbor to get to Borean Tundra or take the boat out of Menethil Harbor in the Wetlands to be dropped off in Howling Fjord.
For Horde, the zeppelin in Ogrimmar leads to Borean Tundra and the zeppelin out of Undercity will take you to Howling Fjord.
Consider camping out your character at one of these spots the night before launch so you can head right over as soon as you have the expansion loaded on your system.
I'm in Borean Tundra and my buddy is in Howling Fjord. How do I get to him?
It will take you some time grab the many flight points that connect these two zones. In the meantime, there is a series of three Tuskarr villages along the coast line that will offer you rides between them via giant sea turtles. You can take them all the way from BorTun to HF or vice versa. Just head to up the coast until you find a dock with a walrus guy. There is a stopover in Dragonblight. A more extensive explanation with pictures and coordinates will be posted here tomorrow.
Where are the new instances I can play immediately?
In Borean Tundra, the 5-man instance is The Nexus. To get there, head to Amber Ledge. It's a mage tower on a hill overlooking the ocean to the west. To get there head north/north-east from Warsong Hold (H) or north west out of Valiance Keep (A).
Once there, take a dragon flight to Coldarra (the icy island to the west) where you land in a mage-created settlement called the Transitus Shield. Take the road north east out of TS to an icy cave, but beware aggro mobs along once outside the shields. Once inside the cave, head to the bottom to enter The Nexus.
In Howling Fjord, you are looking for Utgarde Keep. This is very simple for Alliance, simply head north out of Valgarde keep to the other side of the Vrykul viking settlement. You will see a large stairwell set into the cliff face. Run up it and into the instance. For Horde, head west out of Vengeance Landing and up the lift. From there, follow the road straight west into the instance.
Where's the new Shattrath?
That would be Dalaran. Both Horde and Alliance can use the amenities this neutral city offers. Like Shattrath, there will be no class trainers or Auction House, but there will be Grand Master profession trainers and one-way portals to all the major cities in Azeroth (including one to Shattrath.) There will be mage portal trainers which will come in handy since you can't get to Dalaran before level 74 unless you use a Mage portal. Without a portal, you'll have to wait until level 74. At that point, you can get a quest that will allow you to use a crystal on the floor of the Crystalsong Forest that will take you to the floating city. Once there, bind immediately.
When can I use my flying mount?
Level 77. It used to be a quest, now it's just trainable in Dalaran. For 1,000g (950g with Dalarn faction.) Look on the bright side, no more turtle boats.
Anything else you want to know about to get started on Thursday (that we haven't covered in Ask A Beta Tester or our recent Preparing for Wrath series)?
EDIT: Corrections and updates made.
Arthas awaits and so do your questions. Find the answers you've been looking for that will help you with your journey into Northrend and to level 80 with Wrath 101.