One tip I've learned through my Hardcore worlds is the second you can, get a shield. And always keep a shield in your offhand slot, unless you have a Totem of Undying. Even without an ounce of armor, if you block with your shield you can take the full force of a creeper blast without losing a heart of damage. You can also block all melee and ranged attacks. (Although I believe you still take fire damage from flaming arrows & flaming zombies.)
All you need to craft a shield is 1 iron ingot and 6 wooden planks.