Mage Arcane Talents Builds

Arcane Subtlety (2 ranks)
Reduces your target's resistance to all your spells by 5/10 and all of your Arcane spells cause 20/40% less threat.
D: Up to 2.5% more dps.
E: 20/40% threat reduction on Arcane spells.
S: No effect.
C: Up to a 3% lesser chance of having your Polymorph resisted.
=: Equivalent to gear with 10 spell penetration. This talent is the only way of getting any threat reduction on Arcane spells, aside from much smaller reductions possible through some very expensive enchants.
PvP: *
Raid: **
Level: *
Notes: Not worth taking on its own, but can serve as viable filler.

Arcane Focus (5 ranks)
Reduces the chance that the opponent can resist your Arcane spells by 2/4/6/8/10%.
D: Up to 10% more DPS on Arcane Spells (You'll need to be hitting an enemy 3+ levels above you to get full value out of this talent).
E: No effect.
S: No effect.
C: Works for Polymorph.
=: Equivalent to gear with 10% chance to hit with spells (only for Arcane).
PvP: **
Raid: **
Level: **
Notes: Out of all the first tier Arcane talents, this one has the most all-around usefulness.

Improved Arcane Missiles (5 ranks)
Gives you a 20/40/60/80/100% chance to avoid interruption caused by damage while channeling Arcane Missiles.
D: No effect.
E: No loss of channeled damage due to taking damage.
S: No effect.
C: No effect.
=: The only other ways to reduce lost casting time from damage is via Power Word: Shield, Ice Barrier or similar damage absorption/immunity spells and effects.
PvP: *
Raid: **
Level: *
Notes: While Arcane Missiles are not the best damage spell, they can be viable as while not optimum, they are always useful (at the time of this writing, very few mobs are immune to Arcane).
Use With: Arcane Focus, Arcane Subtlety -- Might as well improve Arcane Missiles all the way.

Wand Specialization (2 ranks)
Increases your damage with Wands by 13/25%
D: Up to 25% more dps... with wands.
E: Wands take no mana.
S: No effect.
C: No effect.
=: Equivalent to getting a better wand; in the event you have the best possible wand, this talent has no equal.
PvP: *
Raid: *
Level: *
Notes: Mages wand as a last resort; it isn't a good idea to spend talent points improving something that (ideally) will never be used.

Magic Absorption (5 ranks)
When you resist a spell, you regain 1/2/3/4/5% of your max. mana and increases all resistances by 2/4/6/8/10
D: No effect.
E: Entirely dependent on the resist gear you're wearing.
S: Slight resistance boost.
C: No effect.
=: No other way to get this effect.
PvP: **
Raid: **
Level: *
Notes: This could be of use in raiding, especially in encounters that rely on a mage having a high level of a resist (e.g. Ragnaros). That said, mages tend to have many other viable, more reliable mana recovery options already.

Arcane Concentration (5 ranks)
Gives you a 2/4/6/8/10% 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%
D: No effect.
E: Up to a 10% mana cost reduction; not quite that much in practice.
S: No effect.
C: No effect.
=: No other way of getting this effect.
PvP: ***
Raid: *****
Level: ****
Notes: Useful mostly for PvE situations, where mana conservation is of consideration. Since it works off of any damage spell, it's one of the most best talents in the Arcane tree. You can cast low mana cost/high efficiency spells (such as Scorch or Frostbolt) until you get a clearcast and then use a high mana cost spell (such as Arcane Missiles, Flamestrike or Blizzard) thus boosting your net mana efficiency. Definitely pick up this talent if you're spending points in Arcane.

Magic Attunement (2 ranks)
Increases the effect of your Amplify Magic and Dampen Magic spells by 25/50%
D: No effect.
E: No effect.
S: Slightly less damage taken from enemy spells (~45 damage at max rank).
C: No effect.
=: No other way of obtaining this effect.
PvP: **
Raid: **
Level: *
Notes: Best used for solo PvP and raiding situations that have frequent amounts of low damage. Note that for periodic effects, such as Shadow Word: Pain or other DoTs, dampen magic only applies to the total damage not to each period, thus greatly lessening its utility against DoTs.

Improved Arcane Explosion (3 ranks)
Increases the critical strike chance of your Arcane Explosion spell by an additional 2/4/6%
D: 6% more crit on AE
E: No effect.
S: No effect.
C: No effect.
=: Same effect can be obtained through gear with +6% crit.
PvP: **
Raid: **
Level: **
Notes: Useful if you see yourself doing a lot of AoE grinding, or tend to play Alterac Valley a lot. Also good for those who wish to get a little extra boost from AE encounters for damage meters in raids.

Arcane Resilience (1 rank)
Increases your armor by an amount equal to 50% of your Intellect.
D: No effect.
E: No effect.
S: Typically this will be about 150-200 extra armor.
C: No effect.
=: No other way to get this particular effect; however, by simply switching around to use gear with more armor you can obtain the same armor bonus.
PvP: ***
Raid: *
Level: *
Notes: It's basically 150 armor for one talent point. Compares favorably with Improved Frost Ward (168 more armor on Ice Armor for 2 talent points). Not that useful for non-PvP situations, but worth it if you're investing in Arcane and have PvP in mind.

Improved Mana Shield (2 ranks)
Decreases the mana lost per point of damage taken when Mana Shield is active by 10/20%
D: No effect.
E: Makes mana shield take less of your mana.
S: Less mana lost translates directly into more mana shields.
C: No effect.
=: No other way to obtain this talent; PvP Gloves give a flat bonus (+285) to Mana Shield absorption.
PvP: ****
Raid: *
Level: *
Notes: Worth picking up for PvP, but not particularly useful outside of PvP.

Improved Counterspell (2 ranks)
Gives Counterspell a 50/100% chance to silence the target for 4 sec.
D: No effect.
E: No effect.
S: No effect.
C: A 4s shutdown vs. casters. Note it can be resisted, however.
=: No other way to obtain this effect.
PvP: *****
Raid: **
Level: **
Notes: One of the best PvP talents there is. Four seconds can oftentimes be an eternity. Certain classes (priests come to mind) can be completely undone with a well timed Counterspell: Silence -- an interrupted heal, no healing for 10 seconds and no casting at all for 4 seconds. You can also cast it before any spells are cast as a blanket silence; this is useful when you're frontloading on a target (presumably sheeped) and want to take away any opportunities they might have for counterplay. Immunity effects such as Divine Shield work through silence, so keep that in mind if you find yourself fighting them.

Arcane Meditation (3 ranks)
Allows 5/10/15% of your Mana regeneration to continue while casting.
D: No effect.
E: Allows for your mana pool to last longer.
S: No effect.
C: No effect.
=: Same effect as Mage Armor; stacks with Mage Armor, however.
PvP: *
Raid: ****
Level: **
Notes: A very solid raiding talent if you're looking to maximize the damage you get out of your mana. If you have a lot of +spirit gear, this talent will be more useful; combined with Mage Armor, you'll have 45% mana regen while casting.
Use With: Mage Armor

Presence of Mind (1 rank)
Instant/3min. cooldown - When activated, your next Mage spell with a casting time less than 10 sec becomes an instant cast spell.
D: Best burst dps increase in the game.
E: No effect.
S: No effect.
C: Allow for instant-cast Polymorph.
=: No way to get this exact effect; 8-piece Netherwind bonus is similar, however.
PvP: *****
Raid: **
Level: ***
Notes: One of the strongest PvP talents, if only for its burst damage potential. It is, however, dispellable.
Use With: Arcane Power, Pyroblast, Flamestrike

Arcane Mind (5 ranks)
Increases your maximum Mana by 2/4/6/8/10%
D: No effect.
E: No effect.
S: More mana can only be good.
C: No effect.
=: Equivalent to getting more +int and +mana gear; in the event you already have the best +int and +mana gear, or don't wish to wear gear just to get more mana, this talent has no equal.
PvP: ***
Raid: ****
Level: ***
Notes: If you're this deep into the Arcane tree and are looking at going deeper, this talent offers a great place to spend points. If you have 6000 mana, this talent will give you about an extra 600 mana.

Arcane Instability (3 ranks)
Increases your spell damage and critical strike chance by 1/2/3%
D: 3% more damage and 3% more crit
E: No effect.
S: No effect.
C: No effect.
=: 3% crit gear and then however much +dmg gear is 3% more for a particular spell.
PvP: ****
Raid: ****
Level: ****
Notes: A very solid talent; note it works for all spells, not just Arcane ones.

Arcane Power (1 rank)
Instant/3min. cooldown - When activated, your spells deal 30% more damage while costing 30% more mana to cast. This effect lasts 15 sec.
D: 30% more damage.
E: Makes your spells less efficient.
S: No effect.
C: No effect.
=: No other way to get this effect.
PvP: ****
Raid: ***
Level: ***
Notes: Combined with PoM, this is the strongest burst damage combo in the game. It is, however, dispellable.
Use With: Presence of Mind.