For Girls (A question about intuition)?

Ok my question is for girls. Would you say you would know if a guy had a crush on you. LIke an innocent kind of crush, nothing threatening, like the kind of crush where he likes you, but you don't. Just by the way he talks, his mannerisms, etc. Like if he talked to you, he would sweat, twist his hair, stutter, smile awkwardly when he tried to make eye contact. Or he would stare at you and when you notice him in the act he would look away. Normally it's perceived in TV, movies, books, that the girl is normally oblivious to his feelings. What do you think, explain, has this ever happened to you? Thanks!