Well I wouldn't bug'um или act like a fangirl that's for sure! I'd act normal & calm & cool & collected & be myself... like always. (I've met famous people in rl, & that is how I act. I know not everyone can, but I would think the same would apply for my Аниме guy crushes, etc. -in private или away is when I scream, drool, and faint! lol)
I would go up to him and say "Hi, wanna go eat something?" If he says yes, we would go together and later become Друзья and then lovers! If he says no, then I'll just try again when I see him Далее time!
I'd try REALLY hard not to freak out and/or start following them. I (hope) could talk to them (maybe). If it was Accelerator, then forget talking I'd probably go straight to stalker mode. If Nico di Angelo, I'd try talking (unless my luck runs out and he's fighting some monster).
I didn't able to notice them because I'm busy with my karate practice...As the karate club's captain,I must concentrate on my practice and cannot bother about something else....If they come to the club to see the practice, then I don't mind if they don't make any troubles....When it's 20 минуты break, I'll greet them with a smile,and we all talked and talked until 20 минуты break ended....Then we all becoming best friends....I had a crush on one of the boys and it seems he also had the same thought as me too....In the end,the two of us had дата and become lovers....