An easy way to do this without losing too much health if you accidentally miss a counter and get hit is during a fist fight. One of the earliest times to get this is pretty much nearer the beginning in White Orchard. You'll find your way to an inn and start talking to the locals in there, asking about Yennifer.
After you have completed the Gwent tutorial, and spoken to Gaunter O'Dimm (The Man of Glass) you end up going outside and are accosted by three thugs who want you to leave, you'll end up in a fist fight with them. You'll want to knock out one of them then the other two will be easy to counter. As you push the other away, then the next enemy will charge up his attack which will be easy to see and counter.
Do that 10 times and it'll unlock. Admittedly you could even do this in the many fist fight tournaments littered around the world areas.