How to know if a guy likes/ Doesn't like you.

Jealousy.

Let's play pretend.

You say to him, "I saw my friend Jonathan last night."

Do his ears perk up? Does his tone of voice change? Most importantly: does he ask, "Who's Jonathan?"

If he's into you – he's gonna care about the other guys you're hanging out with. And unless he's the suavest man on the planet – he's going to reveal he cares (even if he just makes a joke) about what you did with "Jonathan."