Frost Rotation:
Single Target
PS – IT – OB – BS – BS – OB – OB – PS – IT
Multiple Targets/AoE
DnD – PS – IT – PT – BB – HB – BB
Runic Power Usage
With Death Coil, Rune Strike and Frost Strike we have 3 abilities to use Runic Power on. The priority of using Rune Strike still holds true, however using Frost Strike with a Killing Machine proc should give you an equal amount of threat. Don't ever waste Runic Power on Death Coil.
Rime procs
A free Howling Blast is pretty handy in both single target and AoE situations. If you get fortunate enough to gain a Killing Machine proc in AoE situations then use it for Howling Blast, because that will give you an insane amount of threat and also some pretty big numbers on your screen.
Major Glyphs should be
Unbreakable Armor, Obliterate then as yourd 3rd you can c
hoose between Frost Strike and Rune Strike
As for now there are
only 2 viable Sigils in the game:
Sigil of Awareness which is being used most of the time because it boosts your threat by a lot.
Sigil of Deflection use this for fast or very hard hitting bosses.
The usage of those Sigils isn't bound to any spec, they are good for all of them. However Sigil of Deflection can be a major threat loss, so be 100% aware on when to use it. General Vezax is for example a boss where Sigil of Awareness is king.
All of the above comes from Ensidia's DK tanking guide, to be honest you're not the only person in this thread who needs to be schooled so:
http://ensidia.com/home/guides/tanking-death-knight/
NOW WHY THE FUCK WOULD YOU INCLUDE HB IN A SINGLE TARGET THREAT ROTATION