he has acknowledged your existence, good for you! (if you like him)
Nodding up is a sign of acknowledgment and greeting in some cultures. If a guy nods up to a girl, it could be a way of saying "hello" or showing respect.
If you want to be mean, join in their conversation. Or, you could just smile at the guy and walk on by.
She could be flirting with you or just being mean.
It does not necessarily mean anything - he may not be interested in your smiling.
hey I'm pretty sure if he gives you half a smile then he thinks you're cute and might like you.
It could mean that he just wants to be friends or hes scared.
Just try to smile
Well, if this guy see's these girls once and they smile, its just a pleasant human gesture we do to say, Hi, Im waiting in line, too. Now if this guy see's the same girls and they always smile at him, there could be something to it, but if he patronizes the same places he is bound to see the same faces. If he is interested smile back and start some small talk, if he's not just smile back.
They could like you and want to get you know you. Sometimes they just look at you with a flirty smile cause they are a player and may be doing it to get your attention or be playing with you.
It means he's nice, don't look to into it.
act nice and smile.
This guy is most likely attracted to you.