Unholy spec is pretty much just good against magic imo. Respec to frost if you're just getting into DK tanking. Feel free to take a look at my build for a decent, forgiving spec that frontloads so much threat Ulduar10 geared DPS can't jack my aggro. I'll get to rotation in a second. Your gear looks good, other than your weapon. My personal recommendation is to tank through reg HoL and get Seal of the Pantheon from Loken. That should replace the scarab FOR NOW. Once you have that, move on to H DTK. It's easy, and the last boss drops a weapon I love to promote because greenskins need to die! lol! The Masked Mojo Crusher is a troll head on a stick, and nearly as good as the Titansteel Destroyer. In fact, it's better imo due to the added agi which helps us dodge, and DKs are pure avoidance tanks. Next, you should look into the quest reward shoulders from HoS. These can be obtained in either Heroic or Regular mode if I remember right. Pauldrons of Reconnaisance or something of that nature. Nice stats from an easy dungeon. You get the quest from Brann Bronzebeard inside the instance. For your back, grind rep with Wyrmrest and pick up the cloak of peaceful resolutions OR from the added sub-boss in H Nexus you can get Cloak of the Enemy. Very very nice tank cloaks on both accounts. Once you have replaced either of those items (Cloak or shoulder) you can likely throw the scarab trinket back on in place of the Regal Protectorate for added threat or leave that one equipped and switch to the Icebane Girdle for added stamina and (with an eternal belt buckle) two gems. Note: I'm not suggesting BiS items, but rather easiest to get your hands on stuff.
My rotation for Frost tanking:
First pull: DnD, HB, BB, IBF. You'll still have enough RP to rune strike once when it's triggered.
Second round: OB, BS x2 to create death runes, Deathchilled HB. Frost strike, or save the RP for Rune strikes.
Third if you haven't cleaned up yet: OB x 2, HB. Rinse and repeat rounds two and three due to the need to create Death Runes for more Obliterates, and blow IBF every time it's up, typically on the initial pull to lessen the healer's load. This rotation works pretty well for bosses too, so I don't really change anything up.
Note number two: I suggested frost spec because unholy is also an AoE tanking style, but with frost, you're less likely to get your aggro stolen by unruly DPS that doesn't target what you are.
Advice: Unless the DPS is ranged or expertise capped, make sure to turn ALL mobs away from them, and inform them WHY. Why, you ask? Because if the DPS gets parried or dodged, you're the one who's gonna pay for it with a hastened hit from the mob. Any avoided attack on something you're trying to kill hastens the mob's strike by I think it's like 4%. Also, as far as gear goes, Ciderhelm has a stickied gear guide that you can access from this section of the forum. I think it's linked in the first or second post of the HALP!! section, and it's very good. Other than that, practice makes perfect. Happy tanking!
...Thoughts of a philosophical Death Knight...
If death is the inevitable end of life, is life the inevitable end of undeath?