Tutorials/Dungeon mob farming

Dungeon mob farming is pretty simple. You just have to find a Dungeon and make an automatic mob killer around the monster spawner. To find a dungeon you will have to search for one in caves, or use mods.

Preparation
One of the advantages of this method is that it requires very little preparation. You only need 3-4 signs, a couple of pressure plates, a couple of water buckets and a lava bucket. Plus the basic digging gear (Pickaxe, Shovel, etc.)

Finding the dungeon
This is the hardest part of the whole project. Dungeons are fairly rare and full of mobs. First of all, you can set the difficulty to peaceful, so that no hostile mobs appear. Then just start finding a dungeon. It is up to you how you find it, some people just dig around, some people use cartograph. Once you've found a dungeon, start building the killer.

But check what type of mobs spawn because you may have to build it differently if it is a spawner for spiders as they can climb walls.

An easy way to find a dungeon is by pressing F3 and a code will appear above mobs heads. Hostile mobs usually have longer codes. If you see a large group of the same code not changing elevations then it is most likely a dungeon!

Making the killer
First you have to take out all the valuable items inside chests. Make sure that the ceiling is 2 blocks high. Then just dig a 1x1 ditch around the spawner. Pick one corner of the ditch. Then do like this: 1= 1 block deep 2= 2 blocks deep X= 4 blocks deep

1

1

2

2

X 2  2  1  1

Then you should make a lava killer and a ditch that will make goodies go collection point. I'll add it later...

A larger list for mob harvesters can be found here.

More Ways
Another way to make a dungeon trap is to go to the nether and collect 10-20 netherrack and make a flint and steel. About 3-5 blocks away make a square/circle around the spawner and another 3-5 blocks away make another square/circle with netherrack around the first circle/square. Now for the fun part, take your flint and steel and light all the netherrack on fire now when mobs spawn they will walk through the first fire trap and get set on fire, then the second one will finish them off, leaving their drops for you to enjoy!

For dungeons found close to the surface, you can make a trap that will allow mobs to spawn at night and burn during the day from the sun leaving all the goodies for you to collect in the morning without having to worry about anything spawning on you. All you have to do is dig up to the surface and place glass on top so that light will shine in.

Examples
Here is a good example on how to make a dungeon trap using a lava grinder.