It depends what kind of weigh ins. You can do freak weight cuts with day before weigh ins that you cannot do if you are competing the same day (or with wrestling, an hour later). I don’t know much about cutting for day before, but for cutting weight day of, it revolves around cutting stuff out of your diet. For wrestling, I would start watching what I eat the day after a weigh in. 4 days out, I start eating much smaller meals. 3 days out, I start watching how much I drink. 2 days out I pretty much cut food, 1 day out, I pretty much cut water. You have to know a lot about your body and how much weight you can lose doing various things.
I thinking cutting weight teaches amazing body awareness. Eat more meals, but smaller portions. High metabolism helps a lot. I never used a sauna suit as its against the rules in wrestling (highschool and college) and I think it drains you too much to recover in only 1 hour. I would assume day before weigh ins involve a lot more sauna and sauna suits, which sounds like LOTS of fun /sarcasm.