Rankings are based on the following:

1) Frost Bomb
2) Arcane Missiles just before:
3) Arcane Barrage with 4-6 stacks of Arcane Charge
4) Arcane Blast to build Arcane Charge (But remember alwyas try and maintain as much mana as possible!)

Also use these as often as possible!

1) Alter Time
2) Mirror Image
3) Arcane Power
4) Mana Gem

Mage Armor is the self buff used

Stat Importance

Intellect > 15% Hit > Mastery > Haste > Crit