What makes a girl approachable?

I know I'm only 17, so I got plenty of time and it's not really a priority lol, but I never get approached by guys, and I've been told I look friendly, and am usually smiling and bubbly, so I wonder what I'm doing wrong?

Guys, what factors and types of behaviour really make a girl approachable to you?
But not only what makes her approachable, what makes you actually approach her?
Girls, what factors and types of behaviour have you found to work, if any?

Thanks in advance :)
What makes a girl approachable?
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