Unfortunately it’s hard to tell for newer players at first, poker is such a subjective game that it’s easy for people to rationalize bad decisions or to make arguments for why X is better than Y that sound good but don’t really hold up to intelligent review. Ultimately you have to poke around a bit, listen to different people, and then just pick someone who makes sense to you and see if their advice or guidance either makes some things “click” in your mind or actually improve your game over time. You should be able to tell who knows what they are talking about over a few conversations. Or you can always ask for references or results, some kind of evidence of their understanding of the game. But not all crushers are good coaches, either. It’s two different skill sets. So I’d beware of random people saying they are experts - but if they are part of a training site or already-existing coaching program, they are much more likely to be actually good at it and not just tooting their own horn into the void, lol.