Frost Mage leveling build (level 40)

This is a deep Frost leveling setup built around safety first: Improved Frostbolt, Elemental Precision, Piercing Ice, Ice Shards, and Shatter make Frostbolt reliable and hard-hitting, while Frostbite, Improved Frost Nova, Arctic Reach, Cold Snap, Ice Block, and Ice Barrier give you multiple resets when pulls go bad. Ice Barrier is the key level-40 breakpoint: keep it up before pulls so your casts are not interrupted while the shield holds.

The gear prioritizes spell damage without dropping all sustain. Spellpower Goggles Xtreme, Inquisitor's Shawl from Scarlet Monastery Cathedral, Mantle of Lady Falther'ess from Razorfen Downs, Dreamweave Vest/Gloves, Dryad's Wrist Bindings, Red Mageweave Pants, and the PvP cloth belt/boots stack a large amount of general spell damage. The Highlander's boots also add slight run speed, which is excellent for questing and kiting; Horde can use the Defiler counterparts. Hypnotic Blade from SM Library plus Celestial Orb is chosen over a staff for the strong off-hand mana restore, which is valuable while leveling. Icefury Wand adds Frost damage and gives you a mana-free finisher when mobs are nearly dead.

Play by opening at max range with Frostbolt, refresh Ice Barrier between pulls, and kite with Frostbolt slows. Against packs, use Frozen Orb/Living Bomb if available, Frost Nova when enemies reach you, then Cone of Cold or Arcane Explosion while they are controlled. Use Ice Lance while moving, Blink to regain distance, Ice Block as the panic button, and Evocation after combat when low on mana.