Undead Resource Gathering
The Undead harvest resources with two units: Acolytes mine gold, and Ghouls harvest lumber. In order to mine gold, Acolytes must first summon a Haunted Gold Mine over an existing mine. Then, up to five Acolytes may gather around the Haunted Gold Mine and begin adding gold to your reserves, without having to carry it back to the Necropolis. Ghouls will deposit lumber at your Necropolis or Graveyard. Ghouls carry 20 Lumber without having to research any upgrades which is more than any other starting workers.

Scouting
Rush to create a Shade and place it in the enemy town. Newbie players don't even know what a Shade is, let alone how to stop one. Make comments about the enemy town such as "hey you built that building wrong" and "oh you're building those units." It will drive the enemy crazy but of course will give you away to players in the know. This will be very effective early in Warcraft III play and less effective as players learn how to play =)

Blight
Most Undead buildings must be summoned on the Blight, a corrupting influence that turns the land under an Undead settlement to rotted soil. Only two buildings can be summoned on normal land: the Necropolis and a Haunted Gold Mine. Once completed, these buildings generate a radius of Blight, upon which subsequent Undead buildings can be summoned. Each additional building you summon extends the radius of Blight further.

The Necropolis makes far more Blight than other Undead buildings.

Other races can build buildings over the Blight.

The Sacrificial Skull item, available at the Tomb of Relics, can be used to generate a small radius of Blight. It is useful to fast expand (and protect your expansion).

Blight can be dispelled by your enemies once the building that generated it has been destroyed or unsummoned.

Blight Regeneration
An Undead unit will regenerate its health faster when it is standing on, or hovering over Blight. The standard (non Hero) Undead units only regenerate while on the Blight. Off the Blight they do not regenerate either in the day time or at night. However, certain units such as the Death Knight and Obsidian statue can allow Undead units to regenerate health.

[ Click to Enlarge - 174 KB ] TillerMaN heals his Undead Units after a battle.

Expansion Towns
It's best to first Haunt a Gold Mine followed by immediately summoning in a Necropolis next to your expansion. You cannot use Town Portal Scrolls to teleport to Haunted Gold Mines. Halls of the Dead/Black Citadels act as a great tower with a lot of hit points and you can use Town Portal Scrolls to teleport to them. While you don't need a Necropolis at a new town to mine Gold, the benefits of building one are great. You can also use the Necropolis to summon in the 4 additional Acolytes you need to harvest Gold rather than trying to summon them in at your main base and walking them across the map, generally one by one.

Remember, you don't need a Necropolis to mine extra Gold Mines (it just helps for Teleports) so just send a few Acolytes over and summon a Haunted Gold Mine. Surround the Haunted Gold Mine with Ziggurats and then upgrade them to Spirit Towers. This provides both food and protection.

[ Click to Enlarge - 159 KB ] An Undead player's expansion. Two Spirit Towers protect the expansion and the Undead army can teleport to defend it because of the Necropolis.

Building
Acolytes do not need to maintain buildings under construction. Buildings will continue construction on their own (like Protoss) so start a building summoning then move the Acolyte to another task.

Graveyards
Graveyards produce corpses which can be loaded into Meat Wagons or can be used by Necromancers to create Skeletons. Graveyards produce a Ghoul corpse every 15 seconds. The Graveyard can generate up to 5 corpses in a 25 game unit radius.

Building Placement
Ziggurats are also "towers" so place them around your town in defensive formations rather than lining them up like typical farms. Then when you need to create a Spirit Tower the Ziggurats are already in place. Acolytes can repair Ziggurats during battle so keep them near. It's best to wall in the buildings whenever possible with other buildings. Place other buildings around the Ziggurats so that there is less room around the building for Melee users to attack.

Ziggurat Upgrade Trick
When the enemy comes into your town start upgrading a few Ziggurats to make the enemy want to attack them. They typically will either run or start to attack them. Then cancel the upgrades when they leave or right before the Ziggurat is destroyed.

Nerubian Towers/Spirit Towers
One Nerubian Tower is an excellent defense against early rushes. Typically enemy players will run after being hit by a Nerubian Tower a few times (especially Heroes). Many advanced Undead players will not upgrade their Ziggurats to Spirit Towers unless they know someone is about to attack their town. That saves resources. If no one is going to be attacking your town, Spirit Towers will be wasted. In that case it is better to spend money on units.

[ Click to Enlarge - 168 KB ] This setup will save the Acolytes from an early rush.	[ Click to Enlarge - 154 KB ] The town is built in such a way that it's difficult to reach the Acolytes on Gold.

Hero Rush
If your town is Hero Rushed early in the game use your Dread Lord to Sleep the enemy Hero, or use your Death Knight to use Death Coil to heal your Acolytes. If the enemy attempts to attack your Acolytes run them away. Use Death Coil to heal them. If the enemy attempts to kill your Haunted Gold Mine, have the Acolytes come back and repair it or drive the enemy away.

Necromancers
Necromancers are very powerful and useful. Bring them along to create Skeletons out of corpses. Make sure you research Adept and Master Training as well as Skeletal Longevity and Skeletal Mastery.

Meat Wagon and Necromancers Combo
Gather a group of Meat Wagons and Necromancers. Research Exhume Corpses. When you're ready to assault an enemy town bring the Meat Wagons and Necromancers to the enemy town. The corpses from the Meat Wagons will give the Necromancers plenty of corpses to raise.

Obsidian Statues
Bring these guys with your army to heal or generate mana. Most Undead players work this into their strategy. They are also useful later on as Destroyers. "Statues" are very effective in team games so they should be bought on a regular basis.

Dark Ranger/Pit Lord
The Dark Ranger and Pit Lord are great Hero choices for the Undead because they are also Undead and can be healed by the Death Knight's Death Coil ability.

Items
Use Rods of Necromancy early in the game.

Vs. Night Elves

-Demon Hunter - Use Sleep on him. Surround and kill.

-1 Ghoul Rush. Undead players start with a Ghoul. If you know exactly where the enemy Night Elf player is you can send that 1 Ghoul to hit them. They won't even have a Hero or possibly even an Altar yet. This can put you very far behind so don't use it unless you know what you're doing.

-Keeper of the Grove Entangle Rush - Use a Dreadlord to Sleep the Keeper or use the Death Knight's Death Coil to heal any of the units the Keeper hits with Entangling Roots. This can allow you to receive no damage done by the Keeper of the Grove's rush.

-Huntresses - Use Sleep and Abominations. Necromancer's Cripple can also work well. Ghouls can even work with dual Auras and Frenzy if you have enough of them.

-Mass Skeleton - Destroyer's Devour Magic will be perfect to remove all those summoned units