Edit - Jan 2013 - This post dates back to Feb 2010 - That's almost 3 YEARS OLD. I'll do an up to date version soon but in the mean time go to Icy Veins.
Stats
Let's start with the stats. As damage dealers, your key role is to hit stuff, if you ain't hitting it, it's not going down. For. A. Very. Long. Time. Hence, hit rating is one of the highest priorities. For DPS specced DKs, you want to look for 8% to reach your hit cap. That's about 262 rating. Right now, Deme is well over the hit cap and this is something I'll be looking to sort with some dungeon grinding to buy some gems with emblems.
I say that hit rating is one of the highest priorities because it's pretty much on a par with strength. Like warriors our attack power increases 2:1 per strength point and attack power comes in very handy on a fistful of our attacks. You can't over stack strength and we'll come on to how get more of it in the gemming section.
Now, recently, the next stat you decide to stack has slightly switched depending on the content you are running. Enjoying ICC? Stack ArP (that's Armour Penetration - I always forget what it stands for), if you're running older content, go for crit rating here. Then, which ever one you didn't stack first, you can stack next. Let's make that a little clearer.
Running TotC (or older) = Hit > Strength > Crit > ArP
Running ICC = Hit > Strength > ArP > Crit
Following those first 4 stats, it's equal placing for haste and expertise with agility last. Agility isn't a fabulous stat for DKs as a rule so don't worry about it, if you happen to have some, good for you.
GemsOk, confession time. At the time of writing, Deme's gems are pretty sucky. I'm saying this upfront because I've learnt whilst writing this post that I'd been playing around with stuff and I'd made a mess. I'm sorry mum, I promise to head off immediately and spend all those EoTs on new gems. Instead of that new tank set. Essentially I have the wrong meta, and a couple of Ametrine's of the wrong sort.
Basically, for DK DPS, go for Bold Cardinal Ruby or Inscribed Ametrine. These are both strength based gems and the only time you'd think of using another one is if you're not at hit cap. Check out the gems page on WoWWiki for a full listing of all the gems available by colour and stats. Very handy.
Now onto that shameful Meta gem. Now I've read the bits at Elitist Jerks and they recommend the Chaotic Skyflare Diamond or Relentless Earthsiege Diamond. Neither of which Deme is using. More to do with me not reading things on time than anything else. But! Ah ha! She does have the Nightmare Tear in place so that's one thing to tick off, but boy have I messed her up. Now EJ do a great job with all the maths and kudos to you if you can understand it all, but I'm too tired to take it all in so the above is the plan I'll be following with Deme. I'll let you know how I get on.
EnchantsWhat little pieces of magic are going to help you eek out a for more killer points on that vanity dial Recount? You remember grinding all that rep don't you? So you could get all the best enchants?? Well this was why.
Head - Arcanum of Torment - you'll need exalted with Knights of Ebon Hold in Icecrown. These are your brothers and sisters, you should know them! Go see Duchess Mynx in the Shadow Vault.Shoulders - Master's Inscription of the Axe - what's that? Not a Scribe? Oh well sorry you'll have to take Greater Inscription of the Axe then from those Sons of Hodir. Deme has yet to get exalted with them simply because she's never had to.Chest - Powerful Stats - find a friendly enchanter and get him/her to "buff" your chest. Accept no substitutes.Cloak - Greater Speed - remember your stats? Agility was last so grab some haste and make it snappy.Bracers - Greater Assault - 50 AP, simples.Gloves - I can haz more hit cap? Sure you can, whack yourself a Precision enchant if your still looking to hit that magic level. If not, get some Major Strength, another one Deme needs to sort out.Legs - flash those sexy legs at a leatherworker for some Icescale Leg Armour. It's your only option.Boots - Again you add some hit cap here with Icewalker or go for Greater Assault if you've already got your hit sorted.
Remember, every time you upgrade, you need to enchant and gem again. It helps to have a list of all the mats you need for your enchants handy.
Next time, I'll attempt a gear guide, not a BiS, but a "get from dinging 80 to raiding fast" kind of gear guide. Or maybe I won't. We'll see what WoW throws up as ideas.
Suffer Well!
Deme the Doofus.
Further Reading
Elitist Jerks - should be your go to spot, even if you can't understand 1/2 of it, if you get 1 new thing there each time you read, you'll grow as a player. For Unholy DPS, this page is especially great.