So I met a girl through a mutual friend?

We're both church goers. I'm a senior in high school, she's a junior. We go to different schools, and different churches, but I see her around, and I kinda have a crush on her, and I hear she has a crush on me too, but I never know what to say to her. I'm not necessarily looking to go out with her, but I do want to get to know her better. What do I do to go about talking to her, and when I do, what do I talk about? And, please don't tell me to be myself, I already know that.
So I met a girl through a mutual friend?
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