1. Watch a baseball game in which the teams are wearing "throwback" jerseys. Say to self, "Wait a minute, those can't be throwback jerseys. I remember watching games when those jerseys were the regular season uniforms. Oh, that's right, I'm old."
2. Read the list of people up for induction into the baseball hall of fame. Say to self, "Wait a minute, how can all these people be up for the hall of fame already? I have all their baseball cards. Oh, that's right, I'm old."