What I do, which works VERY well for me...
At least two days out from the "event": cut carbs entirely, except for the bell pepper at breakfast. I should clarify, though, that my diet isn't rich in carbs to begin with - only broccoli, bell peppers, green beans, and sometimes tomatoes. These veggies are rich in valuable electrolytes, so I mostly cut them to reduce abdomen size. I can go from flat as a fritter with veins in my abs to looking a few months pregnant with a good healthy serving of veggies. Anyway, drink LOTS of water, 2 gallons or so, and lift hard to deplete glycogen stores. Light, long-duration cardio too if I can manage it.
One day out: Continuing to drink as much water as I can put down, still limiting my carbs to only the pepper in the morning. Take twice my usual Glucorell-R dose with every meal, and 200mg before bed regardless of the presence of food. Also take 1.5 grams of Uva Ursi, and 1.5 grams of Dandelion Root, four times a day. No lifting today, only light, long-duration cardio.
Day of: Rub the sleep out of my eyes upon waking, since I've been up all night going to the bathroom. Still double the Glucorell-R dose, and take the same amounts of Uva Ursi and Dandelion with breakfast. ONLY enough water with breakfast to digest vitamins (this is about 12 ounces for me), and tiny 2 ounce sips throughout the day just to keep my mouth from turning into the Gobi Desert. And it should go without saying, but after the event, I drink water like mad to rehydrate myself.
You're on Thermorexin, aren't you Daisy? That stuff strips the water off nicely, too.