Minecraft Tutorial - How to make an EXP farm
This minecraft tutorials shows you how to make an exp farm. For that you need a mob spawner. If you found a spider spawner, you have to make some things wider as I did in my farm.
It works like this:
The mob spawns and gets into the water.
Through the water he gets to a vertical tunnel.
He swimms to the top of the tunnel and there he gets to a new tunnel.
After that he falls down 21 blocks. Now he has just one heart or less. You can hit him once and you get exp and bones, food or something else!