I've been fighting and cutting for years, and I've found that with full longjohns/plastics/sweatsuit (however you like to do it) and going 10 minutes on treadmill, then 10 in sauna and alternating like that for an hour will cut about 5lbs per hour. Now the closeer you get to finishing the cut, the less water your body has to lose (sweat) and this will decrease accordingly. And you don't need to drink water in the sauna, it defeats the purpose. I usually put 8oz of water in a container and make it last the last 24 hours before weigh ins. Also, eating a few pieces of ice will keep you from killing your whole family a lot of times.
Now with that said, i'm sure someone is going to get on here and say something totally different and argue and all that BS. Most i've ever cut was 20lbs...my buddy, who's wrestled his whole life cut 33lbs that same time.
And it certainly won't hurt to do some practice cuts at some point to see how your body handles it, everyone is different.