Look at you and when you look back he'll look away nervously. He might ask you questions he obviously knows as a convo starter, his friends might tease him when around you, he might do embarrassing things around you, things like that. Pay attention to the little things.
You've came to the right person... oh wait, I'm the one who came to u ;) well, he'd look at u a lot and smile, sometimes when u catch him looking he turns away as if he wasn't looking. or he would act differently when u r around. If u wanted to get in some kind of relationship with him, I suggest u'd approach him as a friend then getting closer & closer. hope it helped. *Sorry if there are any spelling mistakes, English isn't my original language*