If you have trusted friend that is a boy in the conversation he might tell you if the guy is talking about you or not. Another way to find out is to pretend you are about to do something , for example take a drink of water from a water fountain close to him. These are some ways to see if a guy is talking about you.
he will look at stare at you and sit by you
Ask him. That's the best way to know.
If your talking about girl stuff don't know if your talking about guy stuff maybe um Guy wear!
just go with the flow ;)
He will have trouble looking you in the eye, and trouble talking to you.
You ask her.
If the guy doesn't have the guts to talk to you then you start talking to him about sports or something that you know that he might like to talk about.
Another guy will express interest in you by talking to you, smiling at you, winking, perhaps stealing glances at you, etc. === ===
You know if a guy likes you if... he laughs at your jokes when they arent funny you catch him looking at you when your head is turned he always likes talking to you if he teases you (in a cute way)
if he is flirting with you and always talking to you and laughing and wanting to be around you
if he/she don't talk to you while your talking
You can try talking to him ... if that doesn't work - forget him.