How do you tell if a girl is into you when talking to her?

What are the signs that a girl is into you when talking to her? I usually ask her about herself but making an assumption just so I can get her talking and see what she likes. It always seems like my conversations are one sided and they don't ever seem to flow like they do when I talk to guys. Is the guy always supposed to start off and carry the conversation? I've heard of the 90/10 rule where the guy does 90 percent of the talking and the girl 10 but at what point does that turn into 50/50? Girls always answer me and they don't really seem to be annoyed of me ever but like I said, it needs to be a conversation not an interogation. None of the girls I talk to ever ask anything about me in return.
How do you tell if a girl is into you when talking to her?
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