Flirting is more or less just about seeming interested in the person. The best advice I can give is try to find something the girl will want to talk about, and ask about it. Ask open questions, not yes-or-no questions. That way she can say what she's thinking about. Don't be afraid to ask about emotional stuff, just don't ask about sex or anything dark (unless she brings it up, which means she probably doesn't mind).
People like talking about themselves and the stuff they like. If you can get someone to talk about themselves, they'll probably like being around you. Just don't force the conversation. If she doesn't want to talk about something or if she wants to talk about something else, that's just as good.
I don't know what to tell you about whether the girl likes you, but if she's not avoiding you that's a good start. Try to relax and don't think too negatively. Try to enjoy the moment. That's very important, because otherwise there's no point.
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