tl;dr: Approach immediately or risk being looked like a stalker.

I saw a girl but didn't know how to approach her. Waiting for the opportune moment, I followed her in to the library. I then said I thought she was cute and asked for her number.

Later I hear rumors going around that she was stalked by some creepy stranger who tried to get her number. I realized at that moment that I should have just said hi to her the second I saw her instead of waiting for the right moment and risk looking like a stalker.

That was my mistake and one I wanted to share with the community.

Lesson Learned: Approach immediately and don't wait for the opportune moment or you risk freaking the girl out and ruining your chances.