I don't know about deep friendships, as I really don't have the time to maintain all my friendships anymore, but I've become friends with quite a few people by

I don't know about deep friendships, as I really don't have the time to maintain all my friendships anymore, but I've become friends with quite a few people by just picking a few groups on Meetup.com and keep showing up to meetups, do a little chit chat here and there, not a lot, but a little. Eventually people started recognizing me as a regular and I got to know people well enough that they started being friendly to me and asking me to do things outside of meetups. It also helped that I'm generally a friendly person, albeit somewhat quiet. So I just made a consistent effort to keep going to these meetups for a period of two years, and I now know more people than I can keep track of, and made several pretty close friends out of it.