Edit:
The answer below is now outdated since a much easier solution exists – by holding wheat for cows, mooshrooms and sheep, carrots for pigs, and seeds for chicken, animals will follow you.
After rounding up two of each animal, you essentially have an infinite amount of them, since you can breed them.
Sheep also regrow their wool by eating grass, so you don't even need to breed them to have a constant supply of wool.
Here is a modular design to make a series of spawning pads that will spawn animals, and collect them in a central area.
The pads end up being 8x6, except for the ones right next to the collection pit which are 4x6.
The glass area here would be fenced off.
They all drain to this central pit.
Water is placed at the beginning of each trench, and the signs prevent water from moving backwards.
This is a secondary intersection that continues off each main channel.
(The water should be flowing right to the sign
, I might have made the channel too long in my haste.)
And now that Single Player Commands is working with the current version of Minecraft: an aerial view!
gaming.stackexchange.com/users/18/Kevin Yap
If you place torches in a pen, neutral animals will spawn there more because they'll be spawning at night and day, whereas normally they'd only spawn at day.
They'll also be spawning more concentrated there at night.
gaming.stackexchange.com/users/118/Ullallulloo
You could just use wheat by holding it in your hand then go up to the animal.
Once you get its attention (by walking in front of it) it will follow you.
But don't get to far ahead
or else it will lose interest and stop following you.
gaming.stackexchange.com/users/15667/Ryan
In order to make an area that spawns strictly non-aggressive mobs, there is already an answer that covers how to do it.
To summarize, you basically need grass blocks that are well-lit (a light level above 9) in order for non-aggressive mobs to spawn.
Using a system of flowing water between these grass areas you can gather all mobs that fall into the water into a central area.
There are many videos that demonstrate how to do this ( example ).
The following height map shows one such arrangement (1 being the lowest height, 5 being 4 blocks above any 1 block) which will result in water flowing from the top-left corner to the bottom-right corner such that no mobs can jump out of the flowing water: 3333333235555552355555523555555235555552355555523555555222222221 Place your water on the upper-left 3 level tile and your grass tiles on the 5 level in the center with a torch in the middle.
Note that you can tightly pack these units to make a giant mob spawner, although mobs must be within a 9x9 grid of chunks centered on you (or another player) in order to spawn.
Then stand where all your animals drop, pull out a diamond sword and simply chop.
You can also kill them by dropping them from the sky with a sky-spawner .
Lava-based traps might not work as they will likely destroy the wool.
gaming.stackexchange.com/users/1721/Sadly Not
If you look into their eyes while you are holding wheat, they will stare back and when you move they will follow.
I know this works with pigs
but I'm not sure if it works with other animals.
gaming.stackexchange.com/users/19658/Kye
You can use wheat to lure any animals you find into pens.
Just hold the wheat in your hands and any passive mobs (excluding squid?) will follow you.
However, it may take a few tries for you to successfully get the attention of the animal in question.
gaming.stackexchange.com/users/5029/John the Green
If you want to have all the sheep come to you, use this command: /tp @e[type=Sheep]
<your username> You now have lots of sheep.
Ba.
gaming.stackexchange.com/users/118106/DubstepLord1313
Since Minecraft 1.7, you can use a Lead .
gaming.stackexchange.com/users/79446/Hugo Zink
If by best you mean the most challenging, you can build a longway corridor all the way from wherever a good number of them are to your pen, then proceed on pushing them.
I did it before realizing
I just had to have wheat in my hand.
gaming.stackexchange.com/users/13090/Renan
For PE, just dig a hole that is two blocks deep and one block wide and wait for the sheep (and pigs) to come in and build the tunnel thing to where you want to have sheep.
Usually I just keep them in a spare house until I have a pen.
On the other versions, just hold wheat and they follow you.
The best pen on the other versions is a one block deep hole with fencing on the walls of the hole.
Make a one block wide entrance to the gate and since nothing can jump over a fence they can't get out.
gaming.stackexchange.com/users/33376/cassidy
I want to farm sheep for their wool. What's the best way to make them spawn or gather them up into one pen?
Any way to round up animals in Minecraft?
gaming.stackexchange.com
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gaming.stackexchange.com/questions/19546
gaming.stackexchange.com/users/8347/Ryan Detzel
Hold wheat for sheep the the animals will follow you. You need well-lit grass blocks. While the most common suggested way to round up animals, is to make them follow you by using items, few others suggest that the player can make them spawn.
The community lists the requirements for making animals to follow you. A summary of how animals spawn.