1.Start up your Borderlands 2 game.
2.Go to the Extras menu.
3.Click the “Shift” item.
4.Click Sign Up, agree to the terms, and enter your desired email and password, then proceed.
5.Back out to the main menu, then go back to the Shift area.
6.Press  for PS3, or X for Xbox 360 to go the the “My Offers” section, and there you should have a message waiting informaing you that a complimentary Golden Key is available to you now for signing up. Enjoy!
Note: The Golden Key message may take a few minutes, though it should be instant
For those of you wondering what a Golden Key is and what the big deal is keep reading
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The chest you see above is something you should definitely look out for while you are playing Borderlands 2 if you wouldn’t mind some sweet loot. Though not particularly detailed where in, this chest will be located in the city of Sanctuary. According to Gearbox: “This should take you about three hours (two hours to play through the missions leading up to Sanctuary, and one hour for physical recovery after you injure yourself laughing at the impeccably written dialog).”
When opening this chest, you will receive purple loot based on your current player’s level. If you have forgotten the Borderlands system, purple is code for very rare in terms of loot. It is also mentioned by Gearbox that while you can, like with any other weapon in the game trade, sell, or give away the golden chest’s loot, you cannot trade or sell golden keys. Once you have used one of your keys, it is then gone forever. We say one, based on Gearbox’s comment “If you’ve only got one Key…” which leads us to believe if you manage to get more than one golden key, you can stack them for multiple play-throughs.
The item power is based on the level inwhich you open it at. So its best to try and hold off opening it till your a higher level.