Here are some tips for you to level your Death Knight character:
* Stay Geared.
Death Knights get a great set of blues to make up for the high end level 60 gear most people will have going into Outland in The Burning Crusade. I've seen people stick with this gear and not worry about swapping out loot until the very late 60s, but trust me a lot of greens you get from quests and the auction house are much better than the blues from the starter quests. Death knighs are an incredibly gear dependant class so always look for gear like "of the Soldier" or "of the Bandit" pieces, and basically anything else that has stamina, strength, crit rating, attack power, and agility. Most importantly, keep your weapons up to date. Armor plays a big part in how much damage you can rip out, but it is your weapon or weapons that dictate just how much DPS you can do. Whether you're a 2-hander lover or a dual wield player, weapons that are 5-6 levels below you need to be replaced. Your runeblade from the starter quests is great, but consider running dungeon one or two times to get something like this that will last you pretty much until Northerend. At least, you need check for good deals on green weapons from your closest auction house.
* Spec how you love to play, but only to a point.
Because death knights can do respectable DPS in any spec, go for what you love to play but only if it is efficient. If you're leveling the DK as an alt and have a rich main, you have the advantage of dual specs should you chose to drop the ton of gold for the feature while leveling. Personally, I'm a Frost guy. The upfront damage you can rip out with a string of critting frost strikes, it's not the "best" way to level since the self healing isn't too hot. If you're the type of person who has leveled a mage, warlock, or something else by taking down multiple mobs at one time, give Unholy a try. In the late 60s and early 70s it is easily taking down 6-7 or more enemies at a time. If you enjoy soloing everything and don't want to get involved in grouping for a group quest, Blood is your spec. The self-healing you can pump out with blood is enough to keep you alive fighting almost any elite you can come across and makes 3-5 man recommended quests look like a joke.
* Do everything.
If a quest isn't too far out of your way and you know it can possibly lead to more quests, do it. A lot of gamers will claim that you should go and do quests that aren't green to you (which means they are three levels below your current level) because they will give better XP. This is true, however, when every quest you do is yellow on the verge of turning green you can complete them in so much less time and with less time and with less effort and can handle about every elite or group quest yourself. Moreover, everything you don't finish before hitting 80 can be completed at max level earning you tons of gold for an epic flier for your Death Knight.
