Arcane Mage does not rely on crits like Fire Mage, instead, it provides steady DPS, and does not suffer from RNG like Fire, however, in end game fire will provide in most cases higher DPS.

Rotation for Arcane Mage Wotlk

Arcane Mage Priorities

Presence of Mind on Cooldown > Arcane Blast > Arcane Missiles if Missile Barrage procs with 2-4 Arcane Blast Stacks

Tips

Pop cooldowns with 3 stacks of Arcane Blast for maximum damage.

For AOE use Flamestrike and Blizzard.

At the end of a cast, an instant spell can be cast without occurring GCD, this is true for every cast/instant sequence, should be used to maximize DPS.

Use CDs when there is barely any movement or crowd control effects to maximize DPS, the best way to do this is by knowing the fights.