How to Jailbreak iPhone 4, 3GS, iPod touch 4G, 3G, iPad on iOS 4.3.1 using Redsn0w 0.9.6rc9
STEP 1. First you have to download iOS 4.3.1 for your iOS Device.
STEP 2. Using the IPSW file, simply update or restore to iOS 4.3.1 firmware.
STEP 3. Now simply start Redsn0w and point it to the official iOS 4.3.1 firmware file. After iOS 4.3.1 firmware has been verified, simply click on Next to continue.
STEP 4. Now you have to select “Install Cydia” and then click on “Next”.
STEP 5. Before you click on “Next”, make sure your iOS device is turned OFF and PLUGGED IN to the computer.
STEP 6. Now you will be prompted to put your iOS device into DFU mode. For this simply press and hold both Power and Home button for 10 seconds, then release the Power button but keep holding the Home button until Redsn0w detects your iOS Device and the installation starts.
STEP 7. After some time your iOS Device will be restarted.
That’s it. Now your iOS device is fully jailbroken (untethered) on iOS 4.3.1. In this way you can jailbreak iPhone 4, iPhone 3GS, iPod touch 4G, iPod touch 3G, iPad on iOS 4.3.1 using Redsn0w 0.9.6rc9. Click here to download Redsn0w 0.9.6RC9 for Mac, Click here to download Redsn0w 0.9.6RC9 for Windows. Click here to download iOS 4.3.1 for iPhone 4, 3GS, 3G, iPod touch, iPad. Click here to download iTunes 10.2.1 for Mac or Windows. [Via]