IPhone 4 downgrade from ios 6.1.3?

How do o downgrade my iphone the easiest way

To downgrade an iPhone 4 you need to have the SHSH blobs for the firmware version you want to downgrade too. If you never jailbroke your device or used Tiny Umbrella to save blobs then you CAN'T do it.

In Redsn0w, under extras - even more, there's an option to restore to a previous version if you have the blobs.

With an iPhone 4 I'd stay at 5.1.1, http://www.iclarified.com/25182/how-to-downgrade-your-iphone-4-from-ios-6x-to-ios-5x-windows