Death Knight Spec Brief Introduction

This one should be obvious. Having a good talent spec is also very important for being able to output good DPS. Let's start with the talents you will probably want to avoid if speccing for pure DPS purposes:

Blood

- Blade Barrier
- Scent of Blood
- Rune Tap (Great for utility, not so great for DPS unless you have points to spare. As blood, you very well may have points to dump into rune tap, which is a good thing)
- Improved Rune Tap (See above)
- Spell Deflection
- Vendetta
- Mark of Blood (See Rune Tap)
- Bloodworms
- Blood Aura (See Rune Tap, although perhaps not quite so as much)
- Vampiric Blood (See Rune Tap, although perhaps not quite so as much)
- Will of the Necropolis

Frost

- Toughness
- Icy Reach (It seems nice in theory, but you should be in melee in the first place for DPS)
- Lichborne (See Rune Tap)
- Frigid Dreadplate
- Endless Winter
- Chilblains
- Frost Aura (See Rune Tap)
- Unbreakable Armor? (This one is debatable)
- Acclimation
- Hungering Cold

Unholy

- Anticipation
- Unholy Command
- Corpse Explosion
- On a Pale Horse
- Magic Suppression
- Anti-magic Zone
- Unholy Aura (While it's not completely necessary, it's a major buff to the raid in a way that cannot be fully numerically quantified. I'd recommend taking it)

BIG DISCLAIMER: I am NOT saying that you shouldn't take any of these talents at all for DPS'ing, but rather that their priority becomes somewhat secondary until you've taken most of the other DPS talents. Blood talents such as rune tap can be extremely useful and highly recommended for raiding, even though it doesn't functionally increase your DPS.

Here's an example of my frost DK DPS build that I think did rather well in one of my full 25 man Naxx clears:

17/50/0 (4 points to spend wherever you want. Some prefer to dump it all in frost, some like to get up to mark of blood or a point in veteran of the third war)
http://talent.mmo-champion.com/?deathknight=2305020500000000000000000003200505032502112301005101350000000000000000000000000000000&glyph=121013060501

Here's an example of my unholy DK DPS build that I run with great success in most scenarios:

17/0/54 Unholy Build
http://talent.mmo-champion.com/?deathknight=2305020500000000000000000000000000000000000000000000000230200325003115203100223133151&glyph=211214050106