User blog comment:FireGoldsky/Hard Mode/@comment-4674838-20120420194345

My first piece of advice would be to get a full set of Adamantite Armor with the melee helmet, as this will give you a much higher defense rating. Many people have a hard time with hard mode simply because they don't have a high enough defense rating.

Other things you should focus on getting are powerful ranged weapon such as Adamantite Repeater or Crystal Storm, and essential accessories such as Wings (defeat the Wyvern), Spectre Boots, Obsidian Shield and either Sorcerer Emblem or Ranger Emblem. Also, if you're going to use magic, you'll want Mana Flower + stacks of greater mana potions which you can buy from the wizard.

Run out of adamantite ore in your world? You can make a new world, hellevator it, beat the wall of flesh there, smash demon altars and farm more adamantite ore.

Make sure that you completely fill out your health / mana bars if you haven't already, and collect all of the NPCs if you're missing any. You might also want to check out some of the user guides at Category:User Guides. I've written a number of guides specifically about hard mode which can be found there.