Interested in Jailbreak or just having trouble updating to the latest iOS release? You might need to put your iPhone or iPad into DFU (Device Firmware Update) mode first. Some Jailbreaks don't do this automatically, you're often required to do it to downgrade your iOS, and sometimes iTunes gives your errors when trying to update from beta or GM firmware to final release. While DFU mode is straight forward it can also be a little tricky. Here are the steps:
DFU mode, as opposed to Recovery Mode, requires a bit of timing and can take practice to get right, so if at first you don't succeed, don't be afraid to try and try again.
At this point your Jailbreak will take over, or iTunes will show you an alert saying it's detected your iPhone, iPod touch, or iPad and it needs to be restored.
If you're curious as to the difference between DFU mode and and Recovery Mode, Ally Kazmucha explains it this way:
Recovery mode will implement iBoot (basically a portion of the bootloader than runs an integrity check) which will not allow you to downgrade your device. DFU mode will still talk to iTunes but it bypasses iBoot which will then allow you to downgrade firmware.
If you're having trouble and need any extra help, check out our Jailbreak Forum.