Villagers and Villages
Sometimes you will find small villages with a few buildings, inhabited by some rather weird-looking villagers. Villagers occur in plains or desert regions, with different architecture in each.
Most of the buildings are homes, but you will also find a tavern (with a stone slab bar and a fenced-off garden), a blacksmith, a library and/or a church. There will also be wheat farms and a well.
Tip: if you move into a village and want to use the well as a water source, place some blocks below the surface so the water is only 1 block deep.
Villagers are "passive mobs", meaning that they will not fight you. You will encounter five types of villager: farmers (brown), librarians (white), priests (purple), blacksmiths (black apron) and butchers (white apron).
Villagers will wander around doing their stuff by day, and go home at night or when it's raining. You can right-click on a villager to trade with him. Her. It.
Population and houses
Villagers will get together and have babies to increase the population until all the accommodation in the village is full. To increase the number of villagers, you can build more housing.
Villagers aren't very clever, and they get "doors" and "houses" mixed up. To the villagers, a "house" is a door that has more blocks that are open to the sky on one side than on the other. You can increase the village population by adding more doors to the existing buildings, or building new houses for them. Every three valid door/houses you add will increase the maximum population by one.
Build the new housing within about 32 blocks of the well to help the villagers see the housing as part of their village.
Creating new villages
If you build houses well away from any existing village, and somehow get some villagers to move there (perhaps by putting them in minecarts) you can found a new village.
You can trade with villagers using emeralds as currency. The easiest way to get emeralds is to harvest the wheat in a village and sell it to the villagers, but they can also be found in chests or mined. Right-click on a villager to open the trading interface.
Each villager offers one trade, depending on his profession. After you have made the same trade with him a certain number of times, he will get bored of that and start to sell something else.
The best way to gain emeralds is to move into a village and take over the wheat farming duties. You will also find villagers who want to buy many other things.
You will also find a lot of villagers trying to sell stuff. This can be a good way to get diamond tools early in the game if you're lucky, or it can be a really expensive way to get some leather boots.
Some villagers offer to perform a service such as turning gravel into flint or performing an enchantment on an item.
Every now and then, a horde of zombies will attack the village. Will you save the villagers, or will you abandon them to their fate?
In on eof these sieges, large numbers of zombies spawn even if it would normally be too well-lit. They attack the villagers, and at hard difficulty levels, can break down doors to get to them.
If a villager is killed by zombies, he may rise from the dead and join them (50% of the time at Medium Difficulty, 100% on Hard).
The only defence the villagers have against zombies, unless you are feeling heroic, is Iron Golems. These will appear in large villages (16 or more villagers) and help defend against hostile mobs.
You can make an Iron Golem yourself, from 4 Blocks of Iron and a Pumpkin.
It will spring to life the moment you put the pumpkin on!
You gain popularity with a village by trading with the villagers, and you lose popularity by attacking or killing villagers or their golems. If your popularity gets bad enough, the golems will attack you.