These are by no means the only builds possible, but are some of the most popular.  
 
31/20 Arcane/Fire  
 
The cookie-cutter mage spec. Arguably the strongest for general 1v1 combat thanks to the highest burst damage in the game. My personal choice, that I've come back to time and time again.  
 
Core Talents: Improved Arcane Explosion, Presence of Mind, Arcane Power, Pyroblast, Ignite, Impact  
 
Customize: 4/5 Arcane Focus into Improved Mana Shield, Improved Dampen Magic and/or Arcane Meditation  
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Q u o t e:  
 
Arcane Talents (31 points)  
 
# Improved Arcane Missiles - 5/5 points  
Gives you a 100% chance to avoid interruption caused by damage while channeling Arcane Missiles.  
 
# Arcane Focus - 4/5 points  
Reduces the chance that the opponent can resist your arcane spells by 8%.  
 
# Arcane Concentration - 5/5 points  
Gives you a 10% chance of entering a Clearcasting state after any damage spell hits a target. The Clearcasting state reduces the mana cost of your next damage spell by 100%.  
 
# Evocation - 1/1 point  
While channeling this spell, your mana regeneration is active and increased by 1500%. Lasts 8 seconds.  
 
# Improved Arcane Explosion - 5/5 points  
Reduces the casting time of your Arcane Explosion by 1.5 seconds.  
 
# Improved Counterspell - 2/2 points  
Gives your Counterspell a 100% chance to silence the target for 4 seconds.  
 
# Arcane Mind - 4/4 points  
Increases your maximum Mana by 8%.  
 
# Presence of Mind - 1/1 point  
When activated, your next Mage spell with a casting time less than 10 seconds becomes an instant cast spell.  
 
# Arcane Instability - 3/3 points  
Increases your spell damage and critical strike chance by 3%.  
 
# Arcane Power - 1/1 point  
When activated, your spells deal 35% more damage while costing 35% more mana to cast. This effect lasts 15 seconds.  
 
Fire Talents (20 points)  
 
# Improved Fireball - 5/5 points  
Reduces the casting time of your Fireball by 0.5 seconds.  
 
# Impact - 5/5 points  
Gives your fire spells a 10% chance to stun the taget for 2 seconds.  
 
# Ignite - 5/5 points  
Your critical strikes from fire damage spells cause the target to burn for an additional 40% of your spell's damage over 4 seconds.  
 
# Flame Throwing - 2/2 points  
Increases the range of your fire spells by 6 yards.  
 
# Pyroblast - 1/1 point  
Hurls an immense fiery boulder that causes 148 to 195 fire damage and an additional 56 damage over 12 seconds.  
 
# Incinerate - 2/2 points  
Increases the critical strike chance of your Fire Blast and Scorch spells by 4%.  
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33/18 Frost/Arcane  
 
Control, AE damage and snares and survivablity. The other side of the coin, so to speak. Probably the strongest mage spec that isn't the 31/20 Arcane/Fire spec, this spec has the potential to truly shine in Battlegrounds (depending on how they shape up).  
 
Core Talents: Improved Arcane Explosion, Shatter, Frostbite, Improved Blizzard, Ice Block, Cold Snap  
 
Customize: 3/3 Improved Cone of Cold into Piercing Ice, Winter's Chill or Frost Channeling. 2/2 Improved Counterspell into Arctic Reach.  
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Q u o t e:  
 
Arcane Talents (18 points)  
 
# Improved Arcane Missiles - 5/5 points  
Gives you a 100% chance to avoid interruption caused by damage while channeling Arcane Missiles.  
 
# Arcane Concentration - 5/5 points  
Gives you a 10% chance of entering a Clearcasting state after any damage spell hits a target. The Clearcasting state reduces the mana cost of your next damage spell by 100%.  
 
# Evocation - 1/1 point  
While channeling this spell, your mana regeneration is active and increased by 1500%. Lasts 8 seconds.  
 
# Improved Arcane Explosion - 5/5 points  
Reduces the casting time of your Arcane Explosion by 1.5 seconds.  
 
# Improved Counterspell - 2/2 points  
Gives your Counterspell a 100% chance to silence the target for 4 seconds.  
 
Frost Talents (33 points)  
 
# Improved Frostbolt - 5/5 points  
Reduces the casting time of your Frostbolt spell by 0.5 seconds.  
 
# Improved Frost Nova - 2/2 points  
Reduces the cooldown of your Frost Nova spell by 4 seconds.  
 
# Ice Shards - 5/5 points  
Increases the critical strike damage bonus of your Frost spells by 100%.  
 
# Improved Blizzard - 3/3 points  
Adds a chill effect to your Blizzard spell. This effect lowers the target's movement speed to 35% of normal. Lasts 8.50 seconds.  
 
# Cold Snap - 1/1 point  
When activated, this spell finishes the cooldown on all of your cold spells.  
 
# Shatter - 5/5 points  
Increases the critical strike chance of your frost spells against frozen targets by 50%.  
 
# Arctic Reach - 2/2 points  
Increases the range of your Frostbolt spell and the radius of your Frost Nova and Cone of Cold spells by 20%.  
 
# Improved Cone of Cold - 3/3 points  
Increases the damage dealt by your Cone of Cold spell by 35%.  
 
# Ice Block - 1/1 point  
You become encased in a block of ice, protecting you from all physical attacks and spells for 10 seconds, but during that time you cannot attack, move, or cast spells.  
 
# Frostbite - 5/5 points  
Gives your chill effects a 15% chance to freeze the target for 5 seconds.  
 
# Ice Barrier - 1/1 point  
Instantly shields you, absorbing 455 damage. Lasts 1 minute. While the shield holds, spells will not be interrupted.  
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33/18 Fire/Arcane  
 
More consistent damage, plus the dreaded Combusted Blast Wave.  
 
Core Talents: Improved Arcane Explosion, Blast Wave, Fire Power  
 
Customize: Take out points from Combustion and Incinerate and drop 2 into Arcane (maybe into Meditation, Focus or Improved Mana Shield) and then get Presence of Mind.  
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Q u o t e:  
 
Arcane Talents (18 points)  
 
# Improved Arcane Missiles - 5/5 points  
Gives you a 100% chance to avoid interruption caused by damage while channeling Arcane Missiles.  
 
# Arcane Concentration - 5/5 points  
Gives you a 10% chance of entering a Clearcasting state after any damage spell hits a target. The Clearcasting state reduces the mana cost of your next damage spell by 100%.  
 
# Evocation - 1/1 point  
While channeling this spell, your mana regeneration is active and increased by 1500%. Lasts 8 seconds.  
 
# Improved Arcane Explosion - 5/5 points  
Reduces the casting time of your Arcane Explosion by 1.5 seconds.  
 
# Improved Counterspell - 2/2 points  
Gives your Counterspell a 100% chance to silence the target for 4 seconds.  
 
Fire Talents (33 points)  
 
# Impact - 5/5 points  
Gives your fire spells a 10% chance to stun the taget for 2 seconds.  
 
# Improved Fireball - 5/5 points  
Reduces the casting time of your Fireball by 0.5 seconds.  
 
# Flame Throwing - 2/2 points  
Increases the range of your fire spells by 6 yards.  
 
# Ignite - 5/5 points  
Your critical strikes from fire damage spells cause the target to burn for an additional 40% of your spell's damage over 4 seconds.  
 
# Pyroblast - 1/1 point  
Hurls an immense fiery boulder that causes 148 to 195 fire damage and an additional 56 damage over 12 seconds.  
 
# Improved Flamestrike - 3/3 points  
Increases the critical strike chance of your Flamestrike spell by 15%.  
 
# Incinerate - 2/2 points  
Increases the critical strike chance of your Fire Blast and Scorch spells by 4%.  
 
# Blast Wave - 1/1 point  
A wave of flame radiates outward from the caster, damaging all enemies caught within the blast for 160 to 192 fire damage, and dazing them for 6 seconds.  
 
# Critical Mass - 3/3 points  
Increases the critical strike chance of your fire spells by 6%.  
 
# Fire Power - 5/5 points  
Increases the damage done by your fire spells by 10%.  
 
# Combustion - 1/1 point  
When activated, this spell gives your next fire damage spell a 100% critical strike chance.  
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Raid PvE Arcane/Frost  
 
Build purely for raid encounters. Overkill, really, since you can do fine with any of the other builds.  
 
Core Talents: Arcane Subtlety, Improved Arcane Focus, Arcane Power, Improved Blizzard, Winter's Chill  
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Q u o t e:  
 
Arcane Talents (38 points)  
 
# Arcane Subtlety - 3/3 points  
Reduces the threat generated by your offensive arcane spells by 40%.  
 
# Arcane Focus - 5/5 points  
Reduces the chance that the opponent can resist your arcane spells by 10%.  
 
# Improved Arcane Missiles - 5/5 points  
Gives you a 100% chance to avoid interruption caused by damage while channeling Arcane Missiles.  
 
# Arcane Concentration - 5/5 points  
Gives you a 10% chance of entering a Clearcasting state after any damage spell hits a target. The Clearcasting state reduces the mana cost of your next damage spell by 100%.  
 
# Evocation - 1/1 point  
While channeling this spell, your mana regeneration is active and increased by 1500%. Lasts 8 seconds.  
 
# Improved Arcane Explosion - 5/5 points  
Reduces the casting time of your Arcane Explosion by 1.5 seconds.  
 
# Arcane Meditation - 5/5 points  
Allows 15% of your Mana regeneration to continue while casting.  
 
# Arcane Mind - 4/4 points  
Increases your maximum Mana by 8%.  
 
# Presence of Mind - 1/1 point  
When activated, your next Mage spell with a casting time less than 10 seconds becomes an instant cast spell.  
 
# Arcane Instability - 3/3 points  
Increases your spell damage and critical strike chance by 3%.  
 
# Arcane Power - 1/1 point  
When activated, your spells deal 35% more damage while costing 35% more mana to cast. This effect lasts 15 seconds.  
 
Frost Talents (13 points)  
 
# Permafrost - 5/5 points  
Increases the duration of your chill effects by 3 seconds.  
 
# Winter's Chill - 3/3 points  
Increases the power of your chill effects by slowing the target's movement by an additional 10%.  
 
# Improved Frost Nova - 2/2 points  
Reduces the cooldown of your Frost Nova spell by 4 seconds.  
 
# Improved Blizzard - 3/3 points  
Adds a chill effect to your Blizzard spell. This effect lowers the target's movement speed to 35% of normal. Lasts 8.50 seconds.  
 
 
VI. What to Spec First  
 
There are several possible paths up, the one presented below is for a mage who mostly solos and occasionally does instances. If you're running in a set group and know you're going to be AE exping, it's worth going straight to Improved Arcane Explosion and then branching to which tree your prefer. The progression below is probably the simplest and easiest for new mages to acquaint themselves to the class and gain levels rapidly.  
 
End-game PvP builds are great for level 60s, but of limited utility for a level 10 mage, freshly talented, whose main focus is getting levels. In that regard, I present what I believe to be an excellent PvE talent progression. Remember, you can respec your talents for merely 1 gold, making levelling up with one set of talents and then switching at high levels very practical.  
 
Fire is simply better dps and Frost's mana efficency doesn't kick in until high levels (even then, it still kills slower than Frost on net, based on my testing). Thus Fire is best for PvE. Arcane's Presence of Mind and Arcane Power are of limited utility in PvE, making deep focus in Fire a key to a successful mage.  
 
Without further ado, a Mage PvE Talent progression for levels 10-40, listed in order:  
 
Levels 10-14: Improved Fireball the best dps increase you can get at this level, since your Rank 3 Fireball has a base 2.5s casting time, this lets you get them off at 2.0s each.  
 
Levels 15-16: Flame Throwing is nice because range is convenient and lets you get in more fireballs when fighting mobs. Also, Ignite can be put off since your Intellect (and thus crit rate) is still pathetically low.  
 
Levels 17-21: Ignite is a raw damage increase for when you crit.  
 
Levels 22-26: Improved Arcane Missiles because it's time to build Arcane to get Instant Arcane Explosion for use in instances.  
 
Levels 27-31: Arcane Concentration to get clearcasts.  
 
Level 32: Evocation for mana regen once every 10 minutes... at this level it's going to be around 100% of your mana pool, which is very nice. Be warned, it starts fading away from there around level 40ish and at level 60 you can expect about 50% of your mana pool back from Evoc.  
 
Level 33-37: Improved Arcane Explosion is very good for the instances you'll be doing at around this level and up -- Gnomeregan, Razorfen Downs, Uldaman, Temple and on up really appreciate it.  
 
Level 38-39: Incinerate to make Scorch more useful in Instances, since you'll now be able to scorch for a clearcast to fire Arcane Missiles on.  
 
At this point you can continue building in Fire or Arcane or you can spend a gold and respec to whichever combination of talents you prefer.