for a friday afternoon weigh in, you want to start on monday, drink 3+ gallons of water and salt load with a normal diet. you want to try to retain as much water as possible and get your weight bloated up 3-5lbs. tuesday similar amounts of water and salt.
wednesday you want high salt but not as much as on monday/tuesday, still lots of water.
thursday cut the salt out completely and drink about 1 gallon of water, don't eat anything, or if you do make sure it is salt free and protein heavy. the weight of the food is more important than the calories.
check your weight thursday night, if you're very very close you can have a small (4-6oz of water) protein shake.
if you still have a few pounds to go friday morning, you can do heat sessions. 10 minutes submerged in a bathtub with hot as you can stand water. then 15 minutes with the shower running to create a steam sauna. after 25 minutes in the heat, take 5 minutes out of the bathroom to cool down a bit (to avoid stroking out) towel off all the excess water and sweat and salt standing on your skin and check weight.
you should be able to lose about 1.8-2.5lbs per hour at the beginnning, as you get drier you'll slow down your weight loss. if you get very close you can use sour candy to stimulate saliva production and spit out the last pound or so of water.
once you get off the scale after making weight officially, you need to rehydrate immediately, now since you haven't eaten for about 20 hours you'll need to be careful you don't make yourself sick.
we generally rehydrate immediately after stepping off the scale with pedialyte. 1-2 liters of pedialyte, then gatorade diluted with water (1:1).
then start eating salty foods with high carbs, you want to restore your glycogen levels and restore your body's water content to bloat back up to your normal weight to make your gear fit correctly.