How can you tell if someone likes you??

first of all I am a girl. I had a best friend who is a guy. I can't tell if he is cute but I always hear gossips that they admire/like my best friend. And because we are best friend I told him about that. And he wonders why this girls like him. That is still a question until now. For me, if the girl likes a guy. That girl will always find ways to see that guy, to let that guy know that they like him just like, making friends with him in facebook, txting him quotes and etc. and sometimes they make the first move.