How do you know if a girl is into you?

I usually hook up with men. I think i'm bi but it might also be a heteroromantic bisexual kind of thing, but well who cares. Never fell in love with anyone so i wouldn't know. I have mostly kissed girls who said they were bi but appearently were just curious.

Everytime i have sex (with guys) i never get really pleasured, i never cum which isn't that much of a problem but the whole thing of laying in bed with a guy doesn't really turn me on. I never slept with a girl but i know that i do get turned on by girls. I just have NO idea how to get in on with a girl. I don't know how to find out at parties or whatsoever if the girl i am talking to is also into me, which had led to multiple awkard situations created by me.. How do you other girls who like girls know?