Girls, to you, what is the difference between a creepy guy and a guy you want to be friends with?

I joined a singles club recently and last night was my second meeting. I struck up conversation with one of the younger-looking girls and we had a few things in common like we went to the same school, have math-related careers, and like traveling. By the end of the night, she was playfully elbowing me when we were sharing jokes and experiences.

She was 31, I am 30, and she was gorgeous, and I like to think I am good looking enough to get a cute girl. We both came to the event alone. So, what is it that girls distinguish between a creepy guy and a non-creepy guy?