Jailbreak 6.0: For those of you that have already updated to iOS 6, we have some good news. There is already a usable jailbreak if you have an A4 or earlier device, which includes the iPhone 4, iPod Touch 4G, and iPhone 3GS. Read on to learn how to jailbreak these devices.
Note: This only supports the devices listed in the title, any device with an A4 processor or earlier. Additionally, this jailbreak will be tethered, so you will have to repeat the last steps of this tutorial every time you restart your device. Cydia will need to be installed as a separate step also.
Redsn0w 0.9.13dev4 (Download)
iOS 6 IPSWs (Download)
Steps
1. Download and open Redsn0w 09.13dev4.
2.Click “Extras” - “Select iPSW” - Then located the IPSW
3. Click “Back”, then “Jailbreak”
4. Make Sure “Install SSH” is clicked then click “next”
5. Plug in and put your device into DFU mode (See video if confused)
6. Jailbreak device
7. Open Redsn0w again click “Extras” - “Just Boot”
8. Wait for your device to boot up and it should be jailbroken (Cydia will not appear)
Complete Steps 7 & 8 every time your device shuts off to turn it back on.
Install Cydia
Because this jailbreak is still in beta, it will not install Cydia. To install Cydia, follow the directions below.
1. Find your device’s IP address by clicking the disclosure button on your network in Wi-Fi settings
2. Type into Terminal on Mac or cmd prompt on Windows(Windows tip: If Command prompt doesn’t work for you try putty) “ssh root@<your device’s IP address>
3. If prompted about authentication, type “yes” and hit enter.
4. When asked for a password, type “alpine” and hit enter.
5. Once you have connected to your device, type or paste this command into Terminal.
wget -q -O /tmp/cyinstall.sh http://downloads.kr1sis.net/cyinstall.sh && chmod 755 /tmp/cyinstall.sh && /tmp/cyinstall.sh
6. Once this completes, repeat steps 7 and 8 once again to boot tethered, and you should have a working install of Cydia on your device.
SOURCE: JBN