GUYS (or girls) I need your opinion! QUICK!!!?

Okk so there is this guy that goes to my cousins school. I saw a play their in november and he was in it, after wards when I walked out it was just me an my little cousin and he was staring at me when he was lined up against the wall after the play along with the other actors. I looked behind me and no one was in the hallway but me and my little cousin so I KNEW he was staring at me, then I saw him again at the school during this event they had. Now he MIGHT be at the school this Friday for my little cousins play, my cousins know him and his brothers SOOOOO how should I greet him? I would really like to talk to him, but he doesn't know that I exist to my knowledge.... PLEASE HELP!!!! I WILL Pick best answer!