The only requirement is that you feel adventurous and are ready to deal with the implications of a beta iOS on your beloved iPhone.
http://www.cultofmac.com/173666/how-to-install-ios-6-without-a-developer-account/
The text that follows is part of the article at the link, but please be sure you read and understand it.
http://www.cultofmac.com/173666/how-to-install-ios-6-without-a-developer-account/
The text that follows is part of the article at the link, but please be sure you read and understand it.
First, iOS 6, as you know, is still in beta, and a very early beta at that. That means that not everything works as it should, and that you can almost guarantee at least some of your favorite apps won’t function. Second, this firmware is intended for registered developers only. Although it can reportedly be installed on unregistered devices, there’s a very good chance you could be one of the unlucky ones who gets stuck with a device that won’t work.
Finally, we haven’t tested this so we cannot confirm anything. Those who have tested it have reported mixed results; while it works well for some, it doesn’t work for others.