The fact that Death Knights start at a high level means that they have a steep learning curve. This DK leveling guide and its DK leveling spec will give you the skills you need to keep yourself from being one of the 'Death Noobs' people always complain about!
When Wrath launched, skill was not really important to Death Knights; They were overpowered. These days, though, they're a powerful but balanced class. Unholy spec is currently the best for most things, and this includes leveling.
Your Unholy DK leveling spec should be as follows:
Stick with Unholy until you finish getting everything you need from it.
Virulence – 3/3
Vicious Strikes – 2/2
Ravenous Dead – 3/3
Epidemic – 2/2
Necrosis – 5/5
Outbreak – 3/3
Night of the Dead – 2/2
Blood-Caked Blade – 3/3
Unholy Blight – 1/1
Dirge – 2/2
Master of Ghouls – 1/1
Impurity – 5/5
Desolation – 5/5
Crypt Fever – 3/3
Bone Shield – 1/1
Scourge Strike – 1/1
Ebon Plaguebringer – 3/3
Wandering Plague – 3/3
Rage of Rivendare – 5/5
Summon Gargoyle – 1/1
Round out your spec with Blood talents:
Subversion – 3/3
Butchery – 2/2
Two-Handed Weapon Specialization – 2/2
Bladed Armor – 5/5
Dark Conviction – 5/5
This is your DK leveling spec, now let's move on to your DK leveling guide.
General playing and leveling tips:
I'd be surprised if many players with Death Knights do not already know this, but be sure to use keybinds instead of clicking attacks! It can be hard to get used to, but it's sooo much faster. Also, use the mouse to turn quickly by holding down the right mouse button. These two things combined will increase your responsiveness exponentially.
Again, this is something you might already know, but I'll say it anyway: Sell EVERYTHING white quality or better that you do not need on the AH. To speed things up, do it by mailing the items to an alt sitting in a capital city and using that character for everything AH related.
Rest XP is a major bonus to leveling, so do not forget to log out inside an inn or capital city. Use a good questing guide! I'll link my review of the most popular ones at the end of the article. Keep up a food supply; Typically, Death Strike and Frost Presence combined will keep your health high, but when things go bad food can get you going again quickly.
Here we go now, the DK leveling guide specific tips:
Blood Presence is slightly more damage, but Frost Presence means never having to stop and regen health. Frost Presence combined with the regen from Death Strike can allow you to down elites effortlessly.
Do not forget to get your Glyphs ASAP: Ghoul and Death Strike are good for leveling, and the minor glyph that removes the Corpse Dust requirement is very handy as well.
Kiting! When thing go absolutely wrong, you can disease up the mob, set you Ghoul on it, and run away until it dies or you have the runes to Death Strike back to high health. Do not bother with Bone Shield except in emergencies, and do not bother with Death and Decay much either; Both are not worth their run costs in 99% of typical leveling situations. Get around 4% hit, then stack Strength, Attack Power, and ArP over other stats! Stamina is okay but you do not really need it for leveling.
Now, actually playing your Death Knight is pretty simple. But if you do not know the basics, you'll do pretty poorly: Keep diseases on the target and use Death Coil when your runes are all on Cooldown.
The optimal rotation looks something like this at level eighty:
PS – IT – BS – SS – BS – DC – HoW
SS – BS – SS – BS – DC – DC – (DC if Runic Power / Time permit)
But this rotation is more for mobs that are going to last a while. When leveling, just pull with IT, then using PS to get your other diseases up, then simply burning through runes, using Blood Strike for Blood Runes and either Death Strike or Scourge Strike with the rest, depending on whether you need the health from DS Or not.
Finally, do not forget your pets! Use your Ghoul's cooldown often until you get the permanent version, and later when you get your Gargoyle do the same; It's useless if you never use it!