I know it isn't exactly applicable but I've met people in two primary ways. School/college, and jobs, I met my most recent friend at a previous summer job. I've made acquaintances since then at college but I don't really consider them friends. I'm planning on joining a club next semester so I will hopefully meet likeminded individuals there. I'm hoping to do one for my major and one for a hobby.
Also, as far as meeting partners, every time has been something that started as a friendship so most of what I said applied. I met my current girlfriend in high school so that was quite a bit ago.