If you're not sure where to start, just ask about the game last night. Chances are there is some kind of sports game that played, and the guy might be into sports. Those are easy conversation starters. Just beware of mentioning any team names or you'll get caught. For example you would never talk about a Toronto Maple Leafs game if it's the playoffs, because they never make the playoffs. So keep it generic.
You: "How about that game yesterday?"
Random person: "I did not watch it, but I heard Wayne Gretzky scored 4 goals, I taped it, it's going to be amazing to watch!"
(Perfect, the other person has no clue either...)
You: Yeah was epic, it ended up being like 10-5, crazy game!"
Random person: "You bastard! I did not even watch it yet!"
You: "Oh sorry! Hey, we should go out for a beer some time"