Conversation Starters for a guy I like? HELP PLEASE?

I'm gonna make a long story short : So, I really like this guy at my school, we know of each other but never really talked. Like people would ask if I knew him and vice versa and we would both say "yes" cause we do. When we see each other in the hallways we just stare at each other and when people DO ask about me he gets all happy and excited. Nothing much, I mean nothing has ever happened. But I was always too nervous to talk to him in school and nows schools ou and I just need to talk to him. Like its killing me. So I want to message him but idk what to say. Like it'd probably go "hey" "hey" "whats up" "nothing much, you" "same" cool" "yupp" conversation doneee. so I need a goood way to start a conversation and keep it going. Any Help? or Ideas? THANKS