Damage Reduction

In Diablo 3 your Defense Attribute is the most important factor in determining your character's Damage Reduction %. The greater your character's Defense, the greater your Damage Reduction % will be.

Damage Reduction is very important, especially if your character is going to be taking a lot of damage from enemies. If your total Damage Reduction is 0% and monsters are dealing 10 damage to you per hit, you will be losing 10 Life with each monster hit.

However if your total Damage Reduction is 25% and monsters are dealing 10 damage to you per hit you will be losing only 7 Life per hit. This may not seem like a lot, but when you are dealing with hundreds of damage per hit, the reduced damage really adds up.

Damage Reduction may not seem very important or worthwhile in Normal, but as you progress past Normal and Nightmare into Hell and then Inferno you will learn first-hand just how important it is. Without Damage Reduction, monsters will be able to kill you character in only one or two hits. Make sure you learn how to maximize your Damage Reduction %.

Obtaining Equipment that can increase your Defense or Damage Reduction is one of the main ways that you can increase your character's Damage Reduction %. The other main way is to focus on Skills and Runestone Effects that reduce damage taken.

The Following Is A List Of Each Class' Skills That Can Increase Damage Reduction %:

Barbarian Skills That Reduce Damage Taken

Ignore Pain
Relentless 

Demon Hunter Skills That Reduce Damage Taken

Sentry (Guardian Turret)
Shadow Power (Gloom)

Monk Skills That Reduce Damage Taken

Mantra of Evasion (Divine Protection)
Inner Sanctuary (Circle of Protection)
Tempest Rush (Slipstream)
Serenity
Pacifism (Passive Skill)

Witch Doctor Skills That Reduce Damage Taken

Summon Zombie Dogs (Life Link)
Jungle Fortitude (Passive Skill)
Death Trance (Passive Skill)

Wizard Skills That Reduce Damage Taken

Teleport (Safe Passage)
Energy Armor (Force Armor)
Blur (Passive Skill)- Decreases melee damage taken by X%.