How to Prepare for Hardmode in Terraria

Preparing For Hardmode

Dig hellevators to prevent spreading of the Corruption/Crimson. Hellevators are 3-block wide tunnels that prevent spreading of Corruption/Crimson. Why is this crucial? Every biome has something unique about it, and has unique drops, and this will get you far.

Get top-tier pre-hardmode gear. This includes Molten Armor (25 defense for a full set), Night's Edge (42 melee damage), a Molten Pickaxe (can mine Cobalt/Palladium, trust me, you will not regret crafting one or find a drax if you are on 3DS), Sharanga (35 ranged damage, turns all arrows in to Spectral Arrows), Flamarang, Sunfury, and a Phoenix Blaster.

Build a flat surface across the top of the Underworld. This makes your fight with the Wall of Flesh a lot easier.

The Fight With The Wall of Flesh

Summon the Wall of Flesh. To summon the Wall, throw a Guide Voodoo Doll in to a lava pool. If you are playing on mobile version of Terraria, just tap on the doll and it will summon it.

Fight off the Hungry. The Hungry are little, mouth shaped creatures at the front off the wall. Use your Night's Edge or your Sunfury to fend them off. (Note: They will detach from the boss when they are down to 1/3 health.)

Fight the Wall itself. This is when you should use your Phoenix Blaster, Flamarang, and your Sharanga. Your Sunfury also helps for this part too. Make sure to go for either the eyes or the mouth, because those are the only parts of it that take damage.

Starting Out in Hardmode

Collect the loot dropped by the Wall of Flesh. This may include, but not limited to, Pwnhammer, Breaker Blade, Clockwork Assault Rifle, Summoner Emblem, Sorcerer Emblem, Ranger Emblem, and Warrior Emblem. Make sure to have a pickaxe on you, because the loot is in a room with demonite bricks. Don't worry about where to find the room; it will be very close by.

Locate the Hallow. The Hallow is the Corruption/Crimson counterpart, where everything is happy and fun. It is normally on the other side of the world of where the the Corruption/Crimson is. Once you locate the Hallow, dig hellevators on the ends of that biome; it does spread like Corruption/Crimson.

Break Demon Altars. Find Demon Altars in your world, and destroy them with the Pwnhammer. It will bless your world with Cobalt, Mythril, or Adamantite.

Mine Cobalt/Palladium. Cobalt/Palladium is crucial to the start of hardmode, and it can mine Mythril/Orichalcum, make your first set of hardmode gear, etc.