Remember to wear your seersucker suit (no matter the temperature), and make sure your girlfriend brings her giant Kentucky Derby-style hat to go with her bright spring dress. You must be respectful to the opponent, so stand each time a Cardinal hitter comes up to bat. Remain standing until the walk-up song is turned off. Always be conscious of the volume of your voice and your body language. Should a Brewer player strike someone out, hit a home run, or make an impressive defensive play, it is acceptable to quickly stand, clap lightly 3-5 times, and even give a small nod before promptly sitting back down. On the off chance the Brewers actually win the game, smiling is permissible, but make sure to stare straight ahead and avoid any eye contact with any Cardinal fan whatsoever. Should you see any other Brewer fans, it is acceptable to stop, give a firm handshake, and begin walking briskly again. Sorry, I've never been to STL, so can't really tell you what else to do there. I hear the zoo is nice.