Haha - well, try to get 2+ gallons in today and tomorrow. Salt everything today, not tomorrow. This will bloat you up and you'll gain a bit - don't worry! Cut the water at 10 (just caught it's a midday weighin) drinking 1/4-1/2 before that time. Grab some taraxatone from your local GNC. Take one of those at 10 on Thursday. Keep peeing. Sounds simple, but pee even if you don't think you have to. Your body will think it has all this water to lose to acheive homeostasis. It will actually excrete the water past where you started. See where you're at Thursday morning and again around 5pm. If you're still 5-7 out we may have you grab some mag citrate from the pharmacy. You will crap your brains out, but it will get rid of any remaining intestinal bulk.
Other tips: Sauna works wonders if you are close morning of. Get to one and bundle up with trashbags under your sweats. Stop taraxatone about 6 hours prior to weighins so you can begin rehydration as soon as possible.
Rehydration: On the weighins grab 2 bottles of pedialyte and a gallon of water along with a back of your favorite chex mix. As soon as you make weight down 1 bottle of pedialyte. Wait one hour while sipping on the water the whole time. Then mix 1 scoop of whey with the other bottle of pedialyte. This will help you start to get some proteins in your system. Continue to drink the water and start snacking on the chex mix to get the salts back in your system and hold the water. Wait another hour before you get your solid food meal - then pound carbs, fats and proteins like it's your job along with water. You'll want to make sure and get at least another gallon in before you go to bed. This will ensure you don't wake up with a hangover, haha. Seriously that's what it feels like if you don't rehydrate properly! Pizza is my favorite post weigh ins meal, but just make sure you are eating every 2 hours after you weighin to get some bulk back in your system.
I usually like to get another gallon of water and some gatorade in before the start of the show. Other than that, eat fairly normal. Take plenty of gatorade and water with you to ensure you stay hydrated. Also take some easy carb and protein foods to snack on throughout the day. I also like to have a weak gatorade/whey mix between events. Helps keep nutrients in while keeping you hydrated.
Last tip: Don't stray from this plan - it works. EVen if you think you are heavy on Thursday - keep to the plan. I've helped people in the past that have tried to tweak things and it ends up biting them in the ass. Stick to the plan and I can guarantee you will make weight.