A good topic is music. From there you can branch out on what kind of music you like, what artists you prefer, why, etc. Ask about the place or places where he grew up and what he liked to do as a kid. Ask about what he does for a living and if he worked any other kinds of jobs before. Preferences in alchohol, preferences about sports, and what his favorite TV shows are could also be good topics to touch upon. Depending on how you gauge him, you could also try to guess what kind of humor he likes. Learn a few anectdotes. It'll make you look good, especially when you guys are drinking. The best way to start off a conversation is to find common ground or to find an interesting trait about him e.g. a tattoo, a flask, etc., then explore uncommon ground between you and him. Save the humor and the really touchy subjects for when you guys have gotten to know each other. I've befriended total strangers who turned out to be really cool people just by doing this.