Classes
Nine classes, three specs each. Every spec page opens on a cheatsheet: build, priority, stats and the levels that matter.
Warrior
Arms Damagesimple two-handed melee damage; Icy Veins rates it weak solo but strong in groups, and Wowhead suits it to new players.
Fury Damagedual-wield melee damage in groups once you have two good weapons; a slow solo leveller until Flurry (35) and Bloodthirst (40).
Protection Tanktanking dungeons, and solo levelling once Revenge arrives at 14; Icy Veins calls it the fastest Warrior spec to level.
Paladin
Holy Healerhealing a regular party, strongest on one target; solo kills are slow, and real group healing waits for Light's Vigil at 40 (projected).
Protection Tanka Mana tank that holds packs with Consecration and Retribution Aura; also safe solo levelling with sword and board after 20.
Retribution Damagesolo questing with a slow two-hander; ForeverDB and Icy Veins rate it the quickest Paladin to level.
Hunter
Beast Mastery Damagethe easiest and fastest Hunter levelling spec, with the pet tanking; light on area damage, and Wowhead says it brings no group buff.
Marksmanship Damageplayers who want their own shots, burst and range to matter more than the pet's; levels well, but behind Beast Mastery.
Survival Damagea deliberate melee playstyle with traps, not the fastest leveller; it plays at range until its melee kit arrives at 30.
Rogue
Assassination Damagedagger-and-poison melee once you have two daggers and Mutilate at 30; before then it plays like Combat (Wowhead).
Combat Damagethe most forgiving Rogue leveller (ForeverDB): any one-handed weapon, no reliance on poisons or bleeds, and the only real Rogue cleave in Blade Flurry.
Subtlety DamageStealth openers, burst and bleeds, playable from any side with Hemorrhage at 30; strong in PvP, underwhelming at 20 (Wowhead).
Priest
Discipline Healershield-based healing and very safe solo play, with Penance at 30 (Wowhead); weaker group healing and close competition from Holy.
Holy Healerregular group healing with a flexible kit; beginner-friendly (Icy Veins), but mana-hungry and slow to level solo.
Shadow Damageranged damage over time with party healing from Vampiric Embrace; strong one-on-one PvP, but the identity arrives late (Mind Flay 20, Shadowform 40).
Shaman
Elemental Damageranged caster with pack damage from Fire Nova and Magma Totem in groups that carry its mana; Wowhead calls it a poor leveller below 40.
Enhancement DamageWowhead's default early Shaman spec: a slow two-hander, auto attacks doing most of the work, instant indoor Ghost Wolf and Fire Nova on packs.
Restoration Healerhealing a regular dungeon party with Healing Wave and totems; Chain Heal and Riptide wait until 40, and solo kills are slow.
Mage
Arcane Damageburst and strong, low-threat dungeon AoE, if you like managing mana; it has little control or survivability.
Fire Damagethe crit-and-burst playstyle and burst AoE, accepting a weak, crit-starved start; not for a promised early damage lead.
Frost Damagethe safest levelling and kiting spec: slows, freezes and recovery tools for solo pulls and PvP, with steady rather than top damage.
Warlock
Affliction Damagelow-downtime solo questing with DoTs, drains and Life Tap, and cleave on several targets; slow on short fights.
Demonology Damageforgiving, pet-centred levelling with Soul Link's extra safety, especially if you die a lot; it suffers whenever the demon dies.
Destruction Damagedirect casts, burst from two instants and dungeon AoE; Affliction stays the solo-sustain default, as Wowhead finds Destruction slowest solo.
Druid
Balance Damageranged casting with group buffs such as Moonkin Aura, when you can stand still and fund the mana; Feral is the simpler first solo Druid.
Feral Damage Tanka flexible Druid who deals Cat damage or tanks as Bear from one tree, with strong mobility; Icy Veins rates it among the best levellers.
Restoration Healerhealing dungeons for a regular group, with heals over time and the strongest emergency toolkit; slow to level alone.
Specs, hybrids and where else to read
Forever keeps three talent trees per class, with one talent point per level from level 10, so builds that mix two trees are normal, especially while levelling. Blizzard aims for hybrid damage specs to deal about 5% less damage than pure ones, and counts warriors as hybrids (ForeverDB on the hybrid tax). Each class page has a tab for hybrid builds.