Have you ever heard the term “poker face”?
In poker, you don’t learn it in one day, it comes with time, discipline, and a lot of situations where your heart is racing but your face stays calm (like “I'm doing great

”)
That’s why I believe that lying to a real poker player in everyday life is usually a bad idea. They can notice the things most people ignore (I would call them micro-movements).
So here’s the real question: What’s the first thing you look at when trying to read a player?
The first thing we need to observe in a poker player is their body language and micro expressions. Professional poker players are already well "trained" to identify these small signs that less experienced players often miss... subtle changes in posture, gestures, brief facial expressions of surprise, fear, or excitement and confidence... sometimes it's difficult to hide this.
Of course, sometimes this can also be a bluff, so it's not enough to just know the signs; you need to identify whether they are something natural or "forced" to insinuate something to opponents that is not actually the reality.
Anyway... I've already said in another topic that poker is not an easy game, that it involves a lot of statistics and study, and with this "human" aspect it becomes even more difficult.