It does not necessarily mean anything - he may not be interested in your smiling.
She could be flirting with you or just being mean.
when he looks at you and smile
He may be one of those lonely guys you should talk to him and he probably likes you to. = )
That has happened to me a few times. It doesnt always mean that. But maybe he does!
Send him brain waves
It could mean that he finds you attractive or interesting. Smiling back doesn't necessarily mean you are interested, so if it makes you feel weird, you can choose to acknowledge the smile politely and then go about your business.
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.
if he looks at you with a smile on his face...
They like you but they're shy to express their feelings. and maybe they are just staring at something behind you.
laugh at all his jokes. smile when he looks at you. and just be yourself
you either are rlly hot or your had crap next to your eye
Every person is different, but usually a smile and eye contact will get you noticed. Almost everyone looks more attractive when they smile.