Leveling in Northrend was made easier with patch 4.3's reducing the experience necessary by 33%. In addition, many quests in Outland and Northrend were retuned from group quests to soloable, and the major quest givers for instance quests were moved inside the instances in most cases so that players using Dungeon Finder to level through them could turn them in more easily.
These changes make leveling through the oldest content in the game (with the Cataclysm revamps, Outland and Northrend are in fact older content than the 1-to-60 game) easier than it has ever been. That makes now the perfect time to talk about how to level through these 19 levels and get ready for the 80-to-85 content. Since we talked about 1 to 60 two weeks ago, we'll follow much the same format.