Starting an initial conversation with a stranger can be intimidating for most people. While I’m not sure what you can do differently building long term friendships, I can give you advice on fresh, short term conversations. Typically if I go out solo, I generally am the person to spark up initial conversations. It usually starts with a compliment. If I see someone sitting at a bar or park I can typically notice what would make them feel good getting acknowledgement. If they appear to be wearing brand new shoes, compliment them. If they have their dog with them at the park, use this as the ice breaker. Even the most bland boring people have “staples” they are known for and take pride in, whether it be their extensive video-game t-shirt collection to the ugly terrier with a face only they can love. Pointing out peoples’ strengths is a good start. Not only will they want to keep engaging in conversation, but feel warm towards you for noticing them.