You should eat familiar foods at a normal dining hour. The day before a race, incorporate plenty of carbs, but do not stuff yourself with two pounds of pasta. Eat a moderate amount of a well balanced meal (pasta, chicken breast or bolognese sauce, salad, roll is one example) at dinner, and sip both water and sports drink throughout the day. Steer clear of alcohol.
One mistake a lot of people at destination races make is to set out from the hotel for dinner at 7, head to a casual dining restaurant which is busy on weekends, wait 45 minutes or an hour for a table, and all of a sudden, start dinner at 9pm when the alarm clock is set for 5am. Plan ahead and give your body time to assimilate the food and get ready to sleep! You and the line of people behind you at the porta-potties will be grateful.