By Playing the game hardout. It works.
by getting certain armors
no just work for the armor
For info on Halo 3 armors, go to the following link: http://www.gamefaqs.com/console/xbox360/code/926632.html
Not really, special abilities no, its all for looks
You have to earn achievements or get skulls.
Nope. No cheats.
If you mean the achievements, when you get all (Or Most) of them, You Get The Hyabusa Katana Armor, along with other armors.
No. Bungie's gives you the armor as an award. You can't cheat the armor, unless you can cheat them.
you need to acheive different tasks in order to unlock diffferent armor. You also need to get achievements
By playing Halo (online, campaign, and otherwise) you earn credits, which you can then use to purchase armors. You can also complete specialties and get armor that way. All can be accessed through the menu.
you get all the vidmaster achievements on halo 3 and halo 3 odst
by earning achievments- pretty much all u have 2 do is play campaine on legendary(better, faster, and easier wiyh friends playing co-op), and then just play some onilne games.