If you're playing Alliance, that's easy: Catch the boat from Auberdine. It's at the far end of the pier. It's a bit trickier for Horde, unless you're either planning on corpse-running a lot or are a high enough level not to aggro the guards. Fly to Zoram'gar, ride through Darkshore, and catch that same boat. (Be forewarned: Getting on that boat does flag you, as will getting too close to the Exodar.)