Halo 4 Armor Unlocks Guide: Armor Sets, Visors, Stances

Commendations

Commendations are basically achievements you'll have to earn within the game itself—either in single-player or multiplayer depending on their prerequisites.  You can track your commendations from the player menu where you can choose your loadout and armor. Every commendation has several ranks, with Master as the final rank.

Mark VI : Complete the campaign on Legendary (Solo or Co-op)
Commando : Dominion Victory Master
Gungnir : Slayer Victory Master
C.I.O. : Spartan Slayer Master
Ranger : Combat Opportunity Master
Venator : Assassin Master
Protector : UNSC Loadout Master
E.V.A. BRCH : Hail of Death Master
Infiltrator TRAC : Multikill Master
Defender CTRL : Bullet in the Brain Master
Soldier ZNTH : Spartan Spree Master
Recon Surge : Covenant Loadout Master
Warrior Matrix : Forerunner Loadout Master
Enforcer Tribal : Turret Master
Protector Drift : Weapon Master
Orbital AEON : Covenant Destroyer
Aviator Bond : Wheelman Master
Air Assault Verg :Vehicle Master
Venator Raptor : Backstab Master
Soldier Zenith : Spartan Spree Master
Ranger STRK : Protector Master
EOD Shadow : Hail to the king Master
Vanguard Converge : Flag Victory Master
Scout APEX : Oddball Victory Master
Commando FRCT : Flood Victory Master
Contoured Arms CHVR : Perfection Master
Recruit Legs Tiger : Exterminator Master
Twin-Plated AEON : Close Quarters Master
Contoured Legs CHVR : Payback Master