How can i start talkinq to the guy i like?

Okayy so there this boy im startinqq to like.. We go to the same school but the problem is were in different academies.. Which means we dont have the same classes nor share the same lunch. I only see him when i wud walk home... Or wen i wud ditch homeroom to go to his lunch cuz i have friends in there... I have no clue what his name is so in other words hes a total stranger... I wanna talk to him but i have no clue how... Iff anyy one can give me advise wud be nice(: i just wanna know how to approach to the guyy i like but at the same time hes like a total stranger to me :/