I know, that's what's (wow, I don't believe I've ever used two contractions in a row before in my life) with the upcoming Raleigh 8000 and Continental Divide Trail Race this weekend...
Km: Carbo-loading refers to a strategy used to maximize glycogen (energy) stores whereby, you guessed it, you eat a whole bunch of carbohydrates. However, you probably don't need to worry about this for an 8K (or a 10K trail race)... you won't deplete your glycogen stores over this short a race. The most important thing to think about the night before is hydration (and not eating something that will make you sick).
However, while we're on the topic of carbo-loading... there is a lot of "mis-information" out there. For example, the whole notion of pasta dinners the night before races... not exactly necessary. Carbohydrates make you retain water, which makes some people feel bloated, which sounds like an awful way to start 2+ hours of activity. Also, the whole carbohydrate-stripping method... not exactly necessary either. So, what should you do? Run your last "long" run the weekend before the race. Continue to eat normally for the next few days (55-60% from carbohydrates), then (starting about mid-week) increase your carbohydrate intake (70+ %). The day before the race, stick with foods that you know "work" (aka don't make you feel sick), and aim for a good blend of carbohydrates and low-fat protein.Here is a meal plan that I came across.
And, the question that I always had... does it matter which type of carbohydrates you choose? I mean, I know more complex carbohydrates are better for you, but does it matter if you're eating rice or pasta? Well, it turns out that "simple" might not be all that bad for carbo-loading, and it doesn't really matter, and fruits and vegetables have a lot of carbohydrates so you don't need to eat 12 bowls of white rice!
p.s. I ran my marathon PR after brinner at IHOP two days out... I think I was still on a maple syrup high :-)