During the course of your leveling, you will get some extra feats for free. Some are made to fix some math problems with the attack and defense, and some are meant to open up slots for other more interesting feats.
Lvl 1: Melee Training (if you do not have STR as a primary ability)
Lvl 5: Versatile Expertise
Lvl 11: Paragon Defenses
Lvl 21: Robust Defenses
You can add these for free in the Character Builder by clicking on the tiny, yellow House Rule button in the Feats section.