Do you know that most traders and forum users here lies about their dealing in bitcoins. Some exaggerate to their family and friends the unrealistic profit they claim they are making online through bitcoins and these same liers don't tell their losses. Have you ever lied or bragg to your friends about bitcoins.
It depends on what they are trying to achieve by telling you about their trades. If they are not asking for money in return and just want to gloat how great they did so far and show you that they have indeed profited with trading without asking anything in return they could be legit people who are really happy about it and what to share that happiness with you.
However, if they are people who show you how much they made and ask something in return so you could trade like them than they are probably lairs that actually show off so they could rip you off and scam you to make more money. Real traders that make profit do not ask for money to teach, they just keep it to themselves at first or wait until their method is overdone and they can't anymore. Only the scammers ask for money in return.