If i like him or fall in love with him, then i will say thank you and i will ask him do you have girlfriend, first. and if i don't like that kind of guy, then i will say sorry, i already have bf. but we can just meet as friend. sometimes. maybe like that.. it'll be good to both of them. i mean it'll be better. Don't you think? well, it's up to you. :)
To tell if a shy guy likes you try catching him looking at you. Watch him from your peripheral vision to see if he stares at you when he thinks you're not looking. Again, pay attention to the way he talks to you. Check out http://www.wikihow.com/Know-if-a-Shy-Guy-Likes-You for more information.