Most people give up a frightening amount of information in a very short period of time during their social interactions, both on social media and in person. Marital status, children, hometowns, schools, and more are the nuggets of information given out which can end-up in the wrong hands.
Safe topics for making conversation with strangers is not your job, but rather a “safe” hobby, like woodworking, sports, or local history. It’s good to avoid politics and religion.
Most privacy conscious Investigators create a throwaway profile. They learn about something that is not related to their identifying features – cooking, gardening, fishing, etc. – and know enough to pass as a amateur enthusiast. This becomes the first-contact profile used to evaluate a stranger.