You can find a ton of water cut protocols online, but this is what I find works well for me for a 24-hour weigh-in. I usually cut from 138-142 down to 132lbs. In the past, I've dropped weight by only manipulating water and eating less, and frankly, I was miserable. I find manipulating water, salt and carbohydrates to be very effective, and by keeping my fats higher as I pull carbs I don't feel like a zombie until I'm fasting on the last day.
If you've never done a water cut before, know that it will not be comfortable during. You will need to urinate frequently and will be bloated for the majority of it. Don't be surprised when your weight goes up as you increase salt intake. It is normal and you will drop when you pull salt and water.
Watch your evening and morning weight fluctuations. If you know you average 4 lbs of weight loss through the night, try to be close to that before going to bed the night before weighing in. If necessary, I'll sit in a hot bath in the evening and watch something on my laptop until I feel a little light-headed. I'll usually refill the bathtub with hot water as soon as it starts to be a comfortable temperature. A sauna or sweatsuit can work too.
My number one rule for weight cuts is to never panic. I hold water weight when I'm stressed, which makes me more stressed. Make sure you get a good nights sleep before weighing in (as best as you can between bathroom breaks) and try to just relax the night before.

10 Days Out
2 gallons of water
Double sodium intake

9 Days Out
2 gallons of water
Double sodium intake

8 Days Out
2 gallons of water
Double sodium intake

7 Days Out
2 gallons of water
Double sodium intake

6 Days Out
2 gallons of water
Triple sodium intake

5 Days Out
2 gallons of water
Triple sodium intake
Switch to low fiber foods
Reduce carbohydrate intake, increase fats to keep calorie intake the same

4 Days Out
2 gallons of water
Triple sodium intake
Keep fiber low (Aim for under 20g)
Keep carbohydrate intake lower, fats higher
Try to keep your calorie intake the same. Whatever you remove from carbohydrates add to fat.

3 Days Out
3 gallons of water
Limit sodium intake (I aim for 200-400mg)
Keep fiber low (Still under 20g)
Keep carbohydrates lower, fats higher
Add LISS cardio as needed

2 Days Out
3 gallons of water
Limit sodium intake (Aim for 200-400mg)
Keep fiber low (Under 20g)
Keep carbohydrates lower, fats higher
Add LISS cardio as needed

1 Day Out
.25 gallon of water
Limit sodium intake (Under 400mg)
Keep fiber low (under 20g)
Keep carbohydrates lower, fats higher (Ideally the majority of calories will come from fat)
Add LISS cardio as needed
Sweat/sauna/spit as needed in the evening
*All fluid and food should be consumed 16 hours out from weigh-ins*

Day of Weigh-Ins
No water until after weigh-ins
Fast until weigh-ins
Sweat/sauna/spit as needed

Post-Weigh-Ins
SIP Pedialyte and eat fruit for the first 30-45 mins.
Eat foods high in carbohydrates and low in fat
Salt all foods belts-home2