Well, a job or education are obviously the best way to do this. University is amazing for this. Sports work well, e.g. finding an amateur football (soccer) league. Most people hang around before and after.

I've had great success in hackspaces. They're a great place to meet geeky, like-minded people. They can be a bit dead in smaller cities though.

Chat to somebody at a language school and see if they meet up and they'd be interested in speaking to a native speaker. This seems counter-intuitive, but it's about growing your friend circle, and ultimately will probably relapse into the country's tongue. Plus, they're way more sympathetic to your situation.

When you live in a foreign country many things will be different/new, and so you have the perfect excuse to talk to strangers.

"Does this tram go to the (railway) station?", "Do you sell edam?", "How much is this?", "How do I buy a bus-pass?", etc.

I've recently moved from Scotland to Finland, and finding reasons to speak to strangers has not been difficult. Too often they reply in English, but every now and again I pass and have a conversation, albeit brief, entirely in Finnish - it's a little victory.