The easiest way would be...
Go back to Auberdine, take the boat to Menethil Harbor.
In Menethil harbor, grab the flight point, and head out on the road. Follow the road east, then southeast, and after a few more turns it will take you to Loch Modan.
Follow the road south and you will run into Thelsamar. Grab the flight point there as well. Leave Thelsemar to the south, and take the first right you can. This will take you to Dun Morogh. You can look on your map from there to find the way to Ironforge.
In Ironforge, Grab the flight point, head to the gnomish area (farthest east) and go through the portal to the Deeprun Tram. Hop on the tram, take it to the other side, and walk out the portal.
Welcome to Stormwind.
(grab the flight point)