How do you know if you are attractive to the girl?

She will want to get to know you more.

@sailorneptune

That is another good one.

• She doesn't hesitate saying yes when you ask her to hang out. ...
• She's told her friends about you. ...
• She does specific things when you're in a group setting. ...
• She initiates physical touch when you're in public. ...
• Conversations between the two of you seems effortless.

@vince

Very good

most guys are clueless when a women is showing interest in you,

that is something I don't understand