Well, duh, when he/she is [i]papansin[/i]. LOL or always hiding whenever you pass by. Or if your classmates/schoolmates tease you abt him/her. If he stares at you for liek 5mins whenever eur around. LOL. And I'm experiencing it right now. There's a boy in teh intermediate dept. who has a crush on me [i]daw[/i] (his classmates told me) >< And we're actually very good friends. LOL