How to beat the Wither Boss in Minecraft?

Easy. Dig really far down, until you see bedrock, dig a really long 2X1 tunnel horisontally, like super long, around 40-60 blocks long, and make a room at the end made out of Obsidian. Stand in the tunnel, Spawn him in the room, and let him slowly destroy the blocks of the tunnel, and make sure you stock up on healing potions so you can kill hin easier. Get your shiny enchanted diamond sword out, stay deep enough in the tunnel so that you don't get hit but you can hit him, and whack away. The best way for this to be done is by yourself as 1 person alone, as you might hit your friends by standing with them. This personally worked for me, downed the Wither with full health, no potions, prot 1 iron armour, and a sharp 2 dia sword. Its good to invest in a good Diamond sword by enchanting books at level 1 and taking the sharpness or protection books to enchant your armour further, making your weapons semi OP in a short time with little effort.