Karpems is right. Usually the goal is the become nearly glycogen depleted (not a bonk, but slightly more of a carb deficit than usual) and replace the carbs quickly and as fully as possible the night before the event. This is usually done by tapering off your work load the previous week. Right after the ride, eat a high carb (pasta, fruit, potatos), low fat meal.
An Ohio State University study leads the carb-loading idea so far -- and this is how the study went. Ride for 75 minutes at 80% of your MHR. After 75min, do 5x1min MAX EFFORT intervals. Then do 10 sets of 10 leg extensions or flexions on a resistance trainer. Immediately following the effort, consume carbs every 15 minutes for 4 hours (16 equal servings every 15min). How many grams of carbs per serving? Take your weight in pounds, multiply by 3, and divide by 16. For me: (150lbs)*3g = (450g carbs total) / 16 servings = 28g every 15 minutes. Round down your decimal (even if it were 28.99, round down to 28).
Repeat this process exactly 48hrs later, which should end the night before your event.
Good luck with this and don't try it for the first time before an event - practice once. The last thing you want is your stomach, liver, and gastrointestinal system to explode before an important event. Oh yeah, don't do this for events under 2hrs in length.