Knowing if a shy girl wants your attention?

What are the signs? I'm the kinda into this girl who at times can be kinda loud (which I don't mind) and make noises that are totally out of her character, after she does it she glances back at me. I really do want to approach her but we both seem to be shy, I'm the guy and I really like this girl, got to figure something out. A lot of the times I think that I'm not really...good enough. In other words "Why me?".
Knowing if a shy girl wants your attention?
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