I work at a job where you spend a lot of time talking and building a repertoire with the customers - sort of a bartender scenario I guess

My quick mix recipe for making a friend out of a stranger is to wait for a good chance to chat and ask them how they are. Once you get a genuine, detailed response, listen like it's the most interesting and important thing you've heard all week. You don't have to give any advice or anything but really really listen.

Care is in short supply so when people notice that you genuinely care enough to ask how they are and listen they'll really appreciate that. Follow up on some stuff next time you see them to make the conversation start a bit quicker, eg. "Hey ____ did you ever sort out that car trouble?"

You're looking at four or five decent conversations before you're at the point where they'll stop you in the street to say hello and wish you a good day but without fail just being a caring person, someone who checks in and listens without making it weird or intense, has worked for everyone I've met