Frost

Harnessing the powers of the frozen north, Frost Death Knights use their bitterly cold abilities to freeze the very marrow of their enemies bones.

 

An extremely useful tool for overall optimization

http://www.askmrrobot.com

WoWhead Frost guide

http://www.wowhead.com/frost-death-knight-guide

Icy Veins Frost guide

https://www.icy-veins.com/wow/frost-death-knight-pve-dps-guide

Noxxic Frost guide

http://www.noxxic.com/wow/pve/death-knight/frost/