Mage Specs for Levelling

The goal of a levelling spec is to first maximize killing speed while minimizing downtime. I'll offer two levelling specs: one for fire mages and one for frost mages. There isn't much point to an arcane levelling spec as most of the talents in that line aren't conducive to levelling. As to Fire or Frost, it's personal preference for the most part; that said, Fire mages typically kill faster because of Fire's higher dps.

The levelling builds stop at level 39 because, at level 40, I recommend respeccing to a build close to your target level 60 build so that you can learn how to play it well. At level 40 you have 31 talent points, which is enough to get to the bottom any talent tree you desire.

Fire Levelling Spec
Levels 10-14:
Improved Fireball
Why? Best DPS increase available.

Levels 15-16:
Flame Throwing
Why? More range means you'll be able to cast more Fireballs before you get hit.

Levels 17-21:
Impact
Why? A chance to stun means you'll be able to cast more Fireballs before you get hit.

Levels 22-23:
Burning Soul
Why? This will let you get off casts even while getting hit.

Levels 24-28:
Ignite
Why? Get more damage out of your crits.

Levels 29-31:
Master of Elements
Why? Obtain mana back from your crits.

Levels 32-34:
Critical Mass
Why? Crit more often.

Levels 35-39:
Fire Power
Why? A raw damage increase.

Frost Levelling Spec

Levels 10-14:
Improved Frostbolt
Why? The best DPS increase available.

Levels 15-17:
Frostbite:
Why? The chance to root at range means you'll be able to cast more Frostbolts before the mob gets to you.

Levels 18-22:
Ice Shards
Why? Make your crits hit for more.

Level 23:
Cold Snap
Why? Be able to reset Frost Nova on demand for added survivability.

Levels 24-26:
Piercing Ice
Why? Raw dps increase.

Levels 27-28:
Improved Frost Nova
Why? Prereq to Shatter.

Levels 29-33:
Shatter
Why? Benefit from Frostbite and Nova+CoC combos for when the mob gets close.

Levels 34-35:
Arctic Reach
Why? More range means more Frostbolts; also a greater radius for Nova and CoC.

Levels 36-38:
Frost Channeling
Why? Better mana efficiency.

Level 39:
Ice Block
Why? Emergency button worth having even if soloing -- you can use it to wait for a Nova reset or a Blink recharge.