Step 1: Update to iOS 8.1.2 on your iPhone, iPad, or iPod touch using a fresh install if possible
Step 2: Connect your iOS device to your Windows machine, and disable passcode lock and Find My iPhone
Step 3: Download the TaiG 1.2 tool extract it and run it
Step 4: The TaiG tool should automatically detect your iOS device. Once it does, uncheck the 3K Assistant app install option, and click the green Start button
Step 5: Wait until the jailbreak completes and close the TaiG tool when prompted
Step 6: Launch Cydia on your iOS device and enjoy your newly jailbroken iOS 8.1.2 install