Few days at the races can approach the excitement and pure class of an afternoon at Keeneland. Make a reservation a few weeks to a couple months in advance in one of their dining rooms, check the dress code, then show up with an appetite and a betting strategy (a friend always picks number 7, though I don't recommend that).
Keeneland is a beautiful racetrack, and I'm not just saying that because it's on my home turf. I've visited tracks across the country and world and this one is my favorite. The horses and trainers are among the best, the people-watching is phenomenal, and the food ... oh, the food! While I can't eat my favorites anymore, now that I'm a gluten-free foodie, opt for the burgoo in one of the dining rooms, a traditional stew famous for its game ingredient (though chefs don't always include game anymore). The bread pudding is memorably decadent--if you leave without ordering it you should probably be arrested. If you're a bourbon drinker, try the Woodford Reserve. Want a local beer? Opt for the Kentucky Bourbon Ale (or its less-alcohol-concentrated sister, Kentucky Ale).
Don't forget to pick up a program, and watch the horses (and people) in the paddock between each race.
Choose one of many nearby restaurants in Lexington or Midway to complete your day. Favorites in Lexington include Dudley's on Short and Azur. Heirloom in Midway is worth the drive--Mark, the owner/chef, never disappoints, and the beef tenderloin preparation is unlike any I've experienced.