How to reach Northrend from Stormwind [Alliance]
The fastest method of getting to Northrend from Stormwind would be to take the boat in the north dock of Stormwind Harbor. This will get you to Borean Tundra — among the two possible starting zones for WotLK Classic.
The other possible starting zone option is Howling Fjord.
You can travel straight to Howling Fjord if you take the boat from Menethil Harbor within the Wetlands. If you are frantically searching your world map for those Wetlands, you'll find them in central Eastern Kingdoms — just north of Ironforge and Dun Morogh.
As an alternative choice, you may also get to Howling Fjord from Borean Tundra. To do this, you’ll desire to make your way up the new England of Borean Tundra before you reach the Tuskarr village called Unu’pe. From there, you are able to take a boat (turtle) to Dragonblight after which on towards Howling Fjord. Buying WOTLK Classic Gold and wotlk classic boosting can help boost your gear in WotLK, which benefits physical damage dealers and specs that benefit from scaling.
How to reach Northrend from Orgrimmar [Horde]
The fastest method of getting to Northrend from Orgrimmar would be to take the zeppelin in the western tower just away from the southern city gates. This will get you directly to Warsong Hold within the Borean Tundra. Just make sure you don’t go ahead and take Zeppelin to Thunder Bluff, which also leaves in the west tower.
If you need to go to Howling Fjord instead, you can go ahead and take Zeppelin in the tower located just outside Brill and also the Undercity in Tirisfall Glades.
Once you are making it to Northrend, you may also travel between Howling Fjord and Borean Tundra if you take the turtle transports available at the Tuskarr villages of Kamagua and Unu’pe.
Kamagra is located on the west coast of Howling Fjord. Unu’pe is located in the New England of Borean Tundra.