This tip comes to us from performing Strongman Chris Rider, and is from his superb article Tearing A License Plate. Enjoy.
Following a thorough description of the safety requirements for performing this feat (and it really can be a dangerous one, so proceed carefully), comes the basic technique involved. Over to Chris :
Now that we have ourselves protected, it’s time to grab the plate. I personally like to tear plates at chest level, and that is the method I am going to discuss. As a dry run without a plate, place your dominant hand in a hammer style grip. Place the pinky side of that hand just above the bottom of the sternum. Now place the other fist in the same manner below the dominant one so you have the thumb side of the non-dominant and the pinky side of the dominant meeting. Squeeze as hard as you can and push your hands in opposite directions with the top hand going slightly upward and the bottom hand going slightly downward. If you push straight through, the potential for being cut dramatically increases.
Want more? No problem. Head over to the original article, and watch the video below to see it in action. Beautiful.