Leveling up 1–80 in WotLK: route by location

Wrath of the Lich King is the most developed version for leveling: there are almost no “dead” levels. Here's the working route.
1–20: starting area
Go through the entire starting location, don’t miss quests: they give you bags and the first money. At level 10, take professions - “Herbalism + Alchemy” or “Mining + Blacksmithing” will pay off by level 60.
20–40: two zones to choose from
Alliance: Redridge → Twilight Forest → Stranglethorn. Horde: Barrens → Ashenvale → Thousand Needles. Keep quests at the same level and do not go into an area where mobs are 3+ levels higher than you - the time lost is greater than the gain.
40–58: Dungeons Save
At levels 40–50, dungeons open, where in one run they give more experience than an hour of quests: The Deadmines, Scarlet Monastery, Uldaman, Zul'Farrak, Maraudon. Complete the first run for the sake of quests, the rest only if there is a queue.
58–70: Dark Portal
Through the Dark Portal - Hellfire Peninsula, then Zangarmarsh, Terokkar Forest, Nagrand. At 68 you can go to Northrend, but it’s better to reach 70 in Outland: there are fewer competitors for mobs there.
70–80: Northrend
As soon as you set foot on the “Nettle Ice” (Borean Tundra or Kak'Tir Forest), start collecting green items for your future transmog. The locations come in waves: Borean Tundra → Dragonblight → Zul'Drak → Stormpike → Grizzly Hills → Icecrown.
Good to know
- Resting in a tavern gives you a “resting” experience bonus - don’t level up non-stop, you’ll lose up to 30% speed.
- Scrolls/Tome of Cold Weather Flight at level 68 saves hours of running.
- Always take Dungeon Quests - they are repeatable in some dungeons.