Apple iPhone DFU (Recovery) Mode - How to Enter and Exit

Entering DFU (Recovery) Mode

First, ensure that your computer is on and iTunes is running (having iTunes running isn't necessary, but will save a bit of time later). Next, power off your phone by holding down the SLEEP button on top of the unit until the power off slider pops up. Slide your finger across the power off slider, then plug in your iPhone's data cable to both the iPhone and the computer.

Next, Hold both the SLEEP and HOME buttons down for 10 seconds, then release the SLEEP button, but hold the HOME button for 10 more seconds. Your iPhone will have a blank screen, but should be in DFU (recovery) mode.

At this point, iTunes should detect a device in recovery mode and give you the option to resotre your iPhone. If iTunes doesn't detect you iPhone, verify that you don't have OS X 10.6.5 (has issues). If not, try the process again.

Exiting DFU (recovery) mode

Exiting DFU (recovery) mode on your iPhone is a much easier process. Simply hold both the HOME and SLEEP buttons until the iPhone begins to boot up. Release the buttons, and that is it, you are back to normal iPhone operation.