At work. If we want to be really technical we first interacted with each other at a high school track meet (we went to different schools). He yelled "nice ass" as I ran by for high jump and I told him to go fuck himself while flipping him the bird. After seeing different pictures of me from said track meet he realized that I'm who he yelled at. Luckily for me he's much more charming now.
We met online through our "class of 2015" Facebook group. I thought his posts and responses were clever so we started penpaling before classes even started four years ago. Haven't stopped since.
At freshmen orientation for college, while I was having a panic attack trying to register for classes. Didn't date for another 3+ years, though.
Side note for those of you who don't know my backstory: We signed up for a class together. I now teach that class every few semesters and we're getting married on our college campus.