Tutorials/Obsidian farming

Obsidian farming is very useful, especially earlier in the game, when massive caverns have not been found yet. Obsidian farming is accomplished by pouring lava in a trench (must be still) and then pour water so that it flows over top, creating obsidian. This is the favored way to obtain obsidian, because mining or finding obsidian is very risky and dangerous. Obsidian is always near lava (since it's needed to create it), so you must either block off the lava or swim against the current of the water. With farming, all you do is place the lava and pour the water yourself, making it less dangerous. The only dangerous part is getting the lava with a bucket. The easiest way to obtain lava is to travel to the Nether; however, if you can't travel there yet (no portal), you must find a way down to a big cavern, where you will hopefully find lava pools. If you go to the Nether to get some, there are four rules/tips/hints:
 * 1) Look for where you can get down the easiest
 * 2) Bring plenty of pickaxes
 * 3) Never dig straight down
 * 4) Bring many buckets at a time because depending on how close your portal is to the "lava ocean", it might take a while to get there

Building & Usage
A good way to start is to find an open area. If you are building one underground, just dig/mine enough area for at least a 1x7 trench. There are 2 types of farms, but feel free to add to this list:

Basic Farm
This is basically just a trench dug into the ground with walls on either side; nothing special. It gets the job done without all the luxuries. It is simply made by digging (at least) a 1x7 trench in the ground and building short walls on either side. You then pour lava in the trench, making sure that each one will become a source block. Looking at the picture above, you can see that each end has a step; this is required for the water to flow onto the lava. Once the trench has been filled with lava source or spring blocks (when the lava is completely), you can then pour the water onto the "step" and it will flow over the lava, transforming it into obsidian. "Pick up" the water spring with the bucket and begin to mine the obsidian. Note that you need a diamond pickaxe to mine it successfully. For safety, water can be run into the trench before placing the lava down.

Advanced Farm
This type of farm is far more sophisticated than a hole in the ground. What you will need to do to build it is start to make a basic farm. Make the walls one block higher and make a roof (this is optional, and so is glass; it's only for aesthetic purposes). Next, make a small structure at one end of the trench. This is helpful for storing buckets and other supplies. At the other end, make a way to get up to pour water. If you added a roof, you will have to be extra careful when pouring the lava because there is only one way out, which is why it is suggested that you block the flow with dirt so that it does not keep you from pouring the other buckets. Pour the bucket of water in and you're good to go.