Choosing which general to use is a matter of taste. I personally use a Vampire Lord whenever I can, but in a 1,000 point army this neccesitates the use of a necromancer, as the Vampires magical abilities are limited. The main advantage of a Vampire is his incredible combat abilities. If you roll well enough he can easily take down a Chaos Lord, and he can slay other generals before they get a chance to strike back. Some of my opponents are so scared of Vampires that they give their generals the Armour of Protection (4+ special save). The enemy's fear of your Vampire will probably mean they avoid him like the plague.
The disadvantage of taking a Necromancer Lord as the general however, is the points cost. If you intend to include no other characters apart from, say, a unit champion, the he is probably the best choice.
If you are looking to include a larger number of units, then a Liche is probably the right choice. He can take three spells, which is exactly enough to take the two essentials (the Dance and Raise the Dead), and an offensive spell as well.
The first thing to choose is a bodyguard for your general. Although Vampires are capable of taking on small units on their own, and their movement means they can generally avoid trouble, I would recommend putting your general in a unit of skeletons. The advantage of this is the fact that skeletons never break. Although your general could break and flee, the skeletons will stop the enemy from persuing. I tried a Vampire in a unit of mummies, but he kept running away and being cut down (I roll terribly for fleeing units).
For skeletons, I would always recommend taking spears. They can actually cause some damage, especially against Empire troops. I used to take spears as well, but now I rarely bother. The huge amount of strength 4 troops in Warhammer makes the save pointless.
Skeleton horsemen should be used with caution. I use them in small units of five to charge the enemy's flank at the same time as the main unit crashes against the front. Armed with lances they can be used to whittle down units with high toughness, but I find that if they are sent ahead of the main advance, alone, the rank bonus of large units will be enough to cause them to crumble. Another method is to use them in larger units with a Hero and a rank bonus (ten is a good number). This way, they can take on most units, and with the Doomrider Banner (hit automatically when charging) they can cause a unit to rout.
I have never taken ghouls or zombies, but with the release of the new Vampire Counts book soon, I will probably try some out. My main reason for not taking these units is the fact that they can break. I hate to have anything in my army except characters that can break.
If you have enough points, I would recommend taking at least three carrion. These versatile birds can be used in a number of ways. They can take out enemy war machines, or you can plant them behind the enemy units to prevent them marching. Doing so allows you to get off a few more shots with your screaming skull catapult.
A screaming skull catapult is essential. Many people refuse to believe that they can do any damage, but I've managed some incredible things. One skull hit a Chaos general right on his head, caused two wounds, and he failed his panic test and fled! A similar thing happened to a unit of Plague Monks who suffered one casualty and fled off the board! Unfortunatly I don't think they will be available under the nw rules.
Chariots are good fun, but expensive. If you decide to take one, scythed wheels are essential. Sometimes it is worth taking a large unit of basic chariots to draw the enemy fire. Against Chaos though, the only thing that can stop your chariots reching enemy lines is magic.