Here are the steps on how to jailbreak your iPhone.

Jailbreak Requirements:

– A Macintosh System
– Redsn0w 0.9.7b3 by iPhone Dev Team
– Device running iOS 4.2.1
– USBMUXD (http://marcansoft.com/uploads/usbmuxd/usbmuxd-1.0.6.tar.bz2)
– SHSH blobs saved for iOS 4.2 Beta 3
– A copy of iOS 4.2 Beta 3 Firmware (ipsw file)

1. You will need to make sure the device is upgraded to iOS 4.2.1
2. Download usbmuxd and extract to a folder
3. Terminal into the usbmuxd directory and run the following command

chmod +x tcprelay.py
./tcprelay.py -t 22:2222

* This will forward local port 2222 to port 22

4. Connect the phone to the computer and start the Redsn0w program.
5. Point to the official iOS 4.2.1 firmware file and press “Next”
6. Choose “Jailbreak Monte (untether)” and then select the “iOS 4.2 Beta 3″ firmware file
7. Follow the onscreen instructions
8. The iPhone will automatically restart itself once jailbreaked.