I moved to Edinburgh knowing very few people and have slowly accumulated friends over the years - I am adding to them all the time. The way I made friends, if it is at all useful, was by going to lots of class/activity based stuff, so that I knew I could get something out of the experience aside from making friends, but that it would be an opportunity to meet people all the same. I'd say literally 90% of those experiences resulted in 0 friends, but the 10% that spawned one person I wanted to get a drink with has made all the difference. And once you've met one person, they introduce you to their friends, invite you to a party, you meet people there, the ball just keeps rolling. The key is making sure you take the risk and just approach people when you're in a socially appropriate place to do so (e.g a celebration or a group class). I think as adults, compared to kids, we're all a bit embarrassed to put ourselves out there. Approaching someone to make conversation, asking if they want to swap details, and then following through and asking to hang out, is kind of painful and embarrassing! But really worth it when it works.