I don't take credit for the find, but I thought I would pass it along. So every mage knows the spell Arcane Blast - Spell - World of Warcraft It stacks a buff that damage of all Arcane spells is increased by 15% stackable up to 3 times for 45% increase.
Normally your next Arcane spell after the third Arcane Blast would consume the 45% increase buff, but NOT Arcane Missiles - Spell - World of Warcraft So in essence you can get the +45% Dmg buff for each volley of missiles that you launch.
But wait there is more! If you time it just right and cast an Arcane Barrage - Spell - World of Warcraft right after the 4th tick/volley of missiles it will also get the +45% Dmg buff.
What happens when you get the combo off you may ask? I like to call it the "Arcane Shatter"