Want the latest and greatest iOS that won’t make it into the hands of the masses for a few more months? You’ve come to the right place! First, you must be a member of the iOS developer program ($99/year) to download the beta SDK.
1. First download the iOS 7 beta https://developer.apple.com/devcenter/ios/index.action (make sure you get the right version for your phone depending on if you have ATT or Verizon)
2. Make sure you backup your iPhone files by going to iTunes (just click Backup now)
3. After downloading the ios_7_beta__iphone_5_model_a1428__11a4372q.dmg file, double click on it and extract the .ipsw file to your desktop
4. In iTunes, hold down the option and click on “Restore iPhone…”
5. iTunes will now take care of the rest of the iOS beta installation process! The last thing you should do is click “Restore from this backup” when prompted to keep all your old apps
Troubleshooting
If you get the error “This device is not registered as part of the iphone developer program”, don’t fret, you just have to go to the iOS provisioning portal and add your UDID.
By Brian Roizen