Well, we actually met through a matual friend when we went skiing together. (So I suppose it's kind of "fate", anyway...) I think it's more like love at first sight, but the trigger point was when we were enjoying jacuzzi one night, we spent the entire night (12midnight - 6am) talking about philosophical topics (like what we think about life, family, work...). That really made me feel like, wow, we have sooooo many things in common! I think the main key for a girl to fall for a guy is that she could feel that they're on the same track for "big issues" (family, friends, marriage...).
At the early stage when we started dating, we mostly talked about our history: friends from high school, family background... It does help you build up a more "complete" him/her.