An additional note on hit rating and expertise is probably in order here. 8% hit rating is definitely the absolute minimum any build will have, as this prevents misses on special attacks and main hand attacks. The problem becomes when you consider that we need more hit so our spell-like effects won't miss, and dual wielders need still more hit so their offhand won't miss. The jury is still out on exactly how much hit a Death Knight needs beyond that 8%, but I tend to err on the side of caution and generally try to get as close as I can to the spell hit cap as possible without sacrificing too much strength.
Expertise is another sticky subject for Death Knight DPS. Of course, every time you get dodged, you lose DPS. But a good amount of our attacks are spell-like, and thus cannot be dodged at all, making one wonder if it's really worth it to get to the expertise cap. I myself like to hit that expertise dodge cap if I can, but expertise gear for Death Knight DPS is actually rather rare in 5-man content, so you can probably fudge it a bit for now and just focus on making the gap with Naxxramas gear.
All that said, let's check out some of our best choices for gearing up to hit Naxxramas.
If you're looking to put a good helm on your shoulders, go find a Blacksmith. The Spiked Titansteel Helm will definitely cost you a pretty penny, but the stat spread, which includes strength, critical strike rating, and hit rating, can't be beat for a DPS Death Knight, and it includes a Metagem slot, perfect for a Chaotic Skyflare Diamond.
If you don't want to drop the gold on that, You have a couple of options in Heroics. From heroic Azjol-Nerub comes the Chitin Shell Greathelm, which doesn't have any hit rating and has less strength than the above, but does have the 2 gem slots. In addition, Loken in Heroic Halls of Lightning can drop the Planetary Helm. It has lots of strength and agility and hit rating. The agility isn't optimal for a Death Knight since it only gives melee critical strike rating, and it doesn't come with any gem slots, but it's still a solid DPS choice.
Pauldrons of the Lightning Revenant off Ionar in Normal Halls of Lightning, as strange as it may seem, are probably your best bet for a pre-raid shoulder DPS slot, with hit rating, strength, and a red gem slot. If you can't get back to normal dungeons for some reason, you could also go for the Snake Den Spaulders from Heroic Gundrak, but they have haste rating instead of hit rating, making them less desirable. If you have no need of hit rating, they do edge out the Pauldrons of the Lightning Revenant though.
Those of you who read our earlier guide to reputation rewards for Death Knights already know about this one, but it's also worth mentioning: As long as you don't need the hit rating off the pauldrons of the lightning revenant, you may just want to grind revered Sons of Hodir for the Spaulders of the Giant Lords, which are better overall for a Death Knight than the Snake Den Spaulders anyway.
Two choices for a DPS chest pre-Naxxramas stand out. The Engraved Chestplate of Eck from Eck the Ferocious in Heroic Gundrak has lots of hit rating to start out with, and 2 gems slots, perfect for more hit rating, as well as a good chunk of strength.
If you don't need hit rating, consider the Bonegrinder Breastplate from Prince Taldaram in Heroic Ahn'kahet. It replaces the hit rating with critical strike rating, and does have 2 gem slots, so you can even slot of plus hit gems in there if you need to.
The Cast Iron Shackles drop off random trash in heroic Violet Hold, and can apparently be looted from a chest with a key fished up from the waters around Violet Hold. They're a very nice option for DPSing, with plenty of strength and hit rating and even some agility.
If you have some money to spare, though, you may also want to consider getting a Blacksmith to make you some Vengeance Bindings. If you can live without the stamina, these will probably edge out the Cast Iron Shackles for DPS, edging it out in the strength department, replace the agility with the preferable for DK DPS critical strike rating, and nearly matching them in hit rating.
In Heroic Oculus, you'll find your best option for dropped gloves. The Gauntlets of Dragon Wrath come with tons of strength and agility and a sprinkling of hit rating, and should serve you well in Naxxramas. There's not many other pre-raid drops that compare.
If worse comes to worse and these refuse to drop, you can always spend some of your extra Emblems of Heroism on Gloves of the Lost Vanquisher and turn those in for some Heroes' Scourgebourne Gauntlets, which actually still have less strength, but may make up for it with a gem slot, critical strike rating, and a set bonus.
General Bjarngrim in Heroic Halls of Lightjning drops The General's Steel Girdle, which has a good chunk of hit rating along with strength and agility. Once again, the stat spread is lightly less than optimal for a Death Knight, but if you need more hit rating, it is still a very solid choice.
If you don't need the hit rating, the Flame-Bathed Girdle from Keristraza is probably your best Heroic bet. It makes up for the lack of hit rating with plenty of strength and critical strike rating, and even a gem slot if you need to fit in some hit rating. Be sure to add an Eternal Belt Buckle for another gem slot too.
If you're looking for a good pair of pre-raid DPS legplates, look no further than Ingvar the Plunderer in Heroic Utgarde Pinnacle. Staggering Legplates have plenty of strength and a whole lot of hit rating, as well as a red and a yellow gem slot. These really are worth the trouble to get.
If you're having trouble getting those though, you can also grab the Legplates of the Oculus Guardian from Heroic Oculus. They have less strength and hit rating and no gem slots, but they do have some agility.
Here's where it's nice to be a Death Knight. We already have a head start on Ebon Blade reputation, which means we don't have quite as far to go to get the exalted reputation to buy the Death-Inured Sabatons. They have no hit rating, but they're absolutely amazing otherwise, with plenty of strength and critical strike rating, as well as 2 gem slots.
If you insist on not grinding reputation with your own class faction, though, you could settle for the Rift Striders from Anomalus in Heroic Nexus. They have only one gem slot and slightly less critical strike rating than the sabatons, but do equal them in strength.
The Cloak of Bloodied Waters drops off random mobs in Heroic Gundrak. It has no hit rating, but it does have plenty of strength and critical strike rating, making it a very desirable back choice for a Death Knight DPSer.
Despite being from Normal Halls of Stone, Embrace of Sorrow is a strong DPS cloak choice if you need hit rating. It shares the same problem with most other non-tanking cloaks in 5-mans, in that it uses attack power and agility instead of strength and critical strike rating, but it should work in a pinch. You can find the Heroic equivalent in the Cloak of the Gushing Wound from Erekem in Violet Hold. It has less hit rating and attack power, but more agility, which means the Embrace of Sorrow is probably slightly better for a Death Knight.