For the purposes of this guide, it's for Unholy spec Death Knights, as I find frost a wee bit boring and too random.
Anyway. This guide is designed to help you with your Unholy Death Knight's spec, Glyphs and rotation, as much as I can, with the new priority system now in full swing with the new patch.
This spec is the most viable at the moment, up to Cataclysm for Unholy Death knights. The point that's in Unholy Command you can use to your leisure, I just find the Deathgrip CD shortened better for situational purposes. It could go in Resiliant Infection if you really want, but again, it's situational.
DPS in this spec is done in Unholy Presence, as it gives the nice shiny haste that's once again useful for Death Knights, and the Rune Regeneration being sped up lets you hit with abilities quicker.
Current Glyphs that are best for us go as follows:
Glyph of Scourge Strike
Glyph of Raise Dead
Glyph of Death Coil
Glyph of Pestilance
Glyph of Anti-Magic Shell
Glyph of Blood Boil
Minor Glyphs are your own personal preference, but I currently use:
Glyph of Horn of Winter
Glyph of Raise Ally
Glyph of Resiliant Grip
Gems are pretty obvious, pure Strength in most cases, (Bold Cardinal Ruby) Apart from a Sovereign Dreadstone to possibly activate your Helm Meta, which should be a Chaotic Skyflare Diamond. Other choice are of course JC exclusive gems, and a Nightmare Tear.
Enchants I won't go into, as you should know how to enchant your own gear at this stage. DKs don't even need a weapon enchant, we get a free bumped-up Crusader one! Yay!
With the Highbourne being spread everywhere in major cities, we can runeforge stuff. Ironic thing is, The unholy mastery, extra disease damage, is pretty rubbish. If you're above the Hit cap (Elitist Jerks now posts this as 5.83% with the patch) Then reforge all extra Hit into Haste, as more Haste means your Runes will refresh faster.
Okay, the main one. Now it's no longer fixed - it's priority based, but there's still things to consider.
Basically, your opener should be; Blood Tap, IT, PS, SS, FS, SS. Now you want to use "/cancelaura Blood Tap" or it can mess up the generation of death runes on the second rotation. I've bound it to Death Coil in a macro. You should use one Death Coil at the end of your first rotation to remove Blood Tap buff, regardless of whether you have Sudden Doom or not.
Obviously save your main CDs (Gargoyle, Unholy Frenzy) for Bloodlust/Heroism, unless you know they'll come off CD before your raid pops them.
After the opener, the main things to keep in mind are;
You should Death Coil whenever you have the Runic Power to do it, but never when Runic Corruption is up. (don't let Runic Power build to 100 and then spam two/three Death Coils in a row as you might overwrite the current buff, wasting it's usage.)
Use Death Coil whenever Sudden Doom procs, but again not if Runic Corruption is up, hold off a few seconds so you don't waste it and can refresh it.
Other than that, your main rotation becomes a Festering Strike + Scourge Strike nukefest. Ideally, if you use your runes and procs properly, it should be 1 Festering Strike, and 4 Scourge Strikes.
So, trimming that down, it's using the opener when you have to (re)apply diseases, timing your Death Coils right to get maximum Rune regen, and popping Dark Transformation whenever you get to five stack on your ghoul and it's avaliable.
I hope this has been helpful, I've had a few people ask me in guild what to do, and lots of people on the server who aren't in the guild either. If anyone's got comments or suggestions, feel free to flame on and I'll change as needed