Have you ever wondered if you were bluffed out of a hand? One way to know is by looking at the person's face after they take the pot down. Normally they can't help but to crack a smirk. It can be useful for future reference.
Here is a short clip of a smile right after taking a pot down with a bluff:
Clip Source://youtu.be/enQ3n83XR3o
Image Source: https://www.google.com/search?q=sneaky+smile&client=ms-android-verizon&prmd=ivsn&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjwjf6N7a7QAhXDy1QKHfZOAtgQ_AUIBygB&biw=360&bih=560#imgrc=S5KAjjyLN93BSM%3A
Wow that girl is gangsta! I love how she smiles at him to trick him
Yes she is, she also gives a smirk right after taking the pot down