This guy i like...how do i get him to like me?

Ok so there's this guy i like. completely different group of friends etc to me so there's not much chance to get to know him outside school. We've been in the same year for almost 5 years but i neva reali knew him. we've never spoken. But this year we ended up in the same cl and we've been chatting quite a bit and i think i like him. but im kinda shy and i dunno whether he likes me also. sometimes i think he might be showing off around me but i don't know if thats just my imagination. how do i get to know him better cos we only reali talk in cl. and how can I get past that friendly/friends stage? cos right now I think the only potential is for us to be friends. I want to let him no i'd be interested in more.