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noting that the Xbox 360 and Xbox One updates bring the Wither spawn up to 1.8+ of Minecraft, so some Wither videos are out of date and use unreliable methods since the update.
Found an 3x3 with the rear right block missing but it still worked a treat for me in the tutorial nether.
co-ords: X: 30. Z: -7 is the middle with body build on Z: -6 and the heads on Z: -5.
EDIT: 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.