The Power Within is designed to take down your enemy as quickly and efficiently as possible. Your Arcane Blast is the most useful spell at your repertoire, while your Arcane Missiles and Barrage will be your strongest. A lot of utility and trickiness also exists in the spec. For example, if you use Frost Nova or Ring of Frost, your chance to cause critical hits increases by 3 times the normal amount. Also, all of your spell critical hits will refund 30% of the mana due to Master of Elements. Also, Improved Polymorph will allow for a very interesting purpose. Torment the Weak will increase your damage for 3 seconds after the 1st hit.
There are also numerous ways to increase your own damage further, such as Incanter’s Absorbtion, Invocation, and several more such talents. To further your damage, you can use Mage Armor to keep you mana as full as possible, especially with the glyph.
The spell rotation I would recommend, is to use Arcane Blast until you have 4 stacks of damage increase buffs. At this time, if Arcane Missiles is not yet ready, then use Arcane Barrage. You will want to make sure to keep Mana shield up, if you know damage will be coming your way soon, so that way you can gain your Absorption as soon as possible. These Arcane Tactics (haha, sorry, couldn’t help that) will show your enemy your true power within. (Couldn’t help that one either!)