some guys can't really talk when they see a girl..
if they are willing to say something they are stuttering. or their voice is just changing from normal.(like getting really high)

uhm..they are looking at you.. like whenever your around and just gazing in your eyes. or fast turn away when you look back..

they probably have more info bout you, than you can think of :P

(telephone, mobile, adress,a lot of pics bout you.. but you won'tfind out ;) )

but I guess most boys can get control over their feelings not to show you anything unless they think it's right.
they should be interested in you though..