I cant say this is a cast iron rule, but I found that I got a lot better at talking to people when I had no hopes or expectations for them. I had no need for every guy to become my next best friend, or every girl to give me her number. I just relaxed and focused on having conversation. This is very difficult when you want to make friend or flirt with women - you have to let go of that intention until your are comfortable and easy enough in conversation that you don't betray that intention and creep people out.

Just see people and people don't expect anything from them, if something happens then great, if nothing does then hey you have a nice conversation and learned a bit about someone else. People like talking to calm, relaxed people who make them feel at ease - in my experience people avoid excited or jittery people who clearly want something out of the interaction because it makes the feel obligated to respond to that persons wants and it makes them feel uncomfortable.

TL;DR: Don't talk to people expecting or hoping to get anything from them. Converse for the sake of conversation and that leads to good things.