I haven't had a chance to test this yet, but the other video solutions seem to showing sub-optimal methods for killing the Wither. This video also goes into the various ways the Wither can be spawned and how to abuse this to make killing the wither very easy.
It's worth noting that the Xbox 360 and Xbox One updates bring the Wither spawn up to 1.8+ of Minecraft, so some Wither videos are out of date and use unreliable methods since the update.Grrrrandall
pointed out in the comments a location in the Tutorial where you can use this method:
For title update 48 I found a 3x3 located at X84 Y122 Z-53
Please note that this is referring to the ROOF of the Nether - in case you didn't know, the top layer of the Nether is bedrock, just like the bottom layer in the regular world. Thus, you need to get up high in the Nether at the co-ordinates suggested above, and use the bedrock in the roof to trap the Wither.
Credit to Panda4994 on YouTube for this.