WOW Mage: Cast Rotation

Level 1-3 : Cast Fireball from max range and melee the mobs to finish them.

Level 4-5 : Just chain Frostbolt from max range and melee the mobs to finish them.

Level 6-11 : Same as before, but use Fireblast to finish the mobs. If they still live, just cast another Frostbolt / Fireblast or melee them down.

Level 12-25 : Start chaining Frostbolt until your enemy gets close to you. When it does, use Frost Nova (available at level 12) to froze him in place, take some distance and start chaining Frostbolt again.

Level 26-30 : You now have access to Cone of Cold. I like to use it whenever an enemy manages to get close to me because it can proc Frostbite. That will save me a Frost Nova, which has a longer cooldown, and allow me to cast another Frostbolt that will most likely crit, thanks to Shatter.

If it doesn't proc Frostbite, i will then use Frost Nova followed by a Frostbolt or i will use Fireblast to finish the mob, depending on its hp left.
The goal, with Cone of Cold, is to save Frost Nova as much as possible.

Level 30-39 : Same as before, excepted Cold Snap is available, meaning you can Frost Nova your enemies two times in a row to burst them even faster.

Level 40-44 : Ice Barrier is available. You'll have to worry less about being hit and will be able to cast your Frostbolt wihout pushbacks while the barrier is active.

Level 45-49 : You'll start criting even more. Fingers of Frost will speed up your killing tremendously.

Level 50 : Your Water Elemental is now available. I suggest saving it for tricky situations (elites, pack of mobs, etc..).

Level 51-59 : Now you have to monitor the Brain Freeze proc. When it does, launch the Fireball after your nukes. Don't interrupt your spells for a Fireball unless it can finish off your enemy.

Level 60-65 : Deep Freeze is available, meaning you can stun your enemies when they are frozen in place. I suggest stunning them when Frost Nova / Frostbite is about to break.

Level 66-70 : Killing machine : ON. Ice Lance is a crazy spell. It is instant cast, costs almost nothing and does HUGE damage if your enemy is frozen. As soon as you see the enemy frozen in place, be ready to launch an ice lance right after your frostbolt. Those 2 spells critting in a row will remove like 60% of your enemy's health.

Level 71-74 : Your spells can now stun, thanks to Impact. If an enemy manages to gets close to you, it means either that you were AFK or that he is immune to movement-imparing effects