My good luck charm is to eat my way around the world at Epcot for lunch (who doesn't love shrimp tacos, barramundi, and escargots pre race) and have a pizza around 6 for dinner. Get's me my best time every time (nothing to do with my training).
Like was said, you need to be hydrated, extra hydrated actually, because it's humid and very warm....unless it is raining. Ha!
Seriously though, know what is good for your body...you do not want anything that can mess your stomach up. I know me and pizza mesh well, so I go for PIZZA!