One thing you will notice about the new iOS 6 for iPhone, iPad and iPod Touch is that it has a really large file size. Even with the over-the-air delta updates the file size can go anywhere from 600 MB to even up to 1 GB depending on your device.

The easiest way to update to the new OS is to download iOS 6 via OTA (Over The Air). Open Settings > General > Software Update. It's that easy.
However a lot of users have been facing an issue where the over-the-air update is stuck in a loop or simply fails at some point. The good thing is, that we have a solution for this.
- First download and install iTunes 10.7 from Apple.com
- Head over to felixbruns and download iOS 6 IPSW for your device from the drop-down menu
- Backup your iPhone with iCloud or iTunes
- Plug in the iPhone and connect it to iTunes to restore the iOS 6 IPSW.
- Click on the iPhone icon and click on "Restore" while holding the Shift/Option key.
- Locate the IPSW and let the restore begin.
This is the easiest and probably the most hassle free method to update your iPhone to the latest iOS 6 in the fastest manner possible.