Start about a week out. Up your water intake to 2 gallons and keep it at that for 3 days. The next day drop it down to 1 gallon. The next day drop it to a half gallon. From there on out play it by ear, but don't go over a half gallon. The last day you should be taking in very little water if any, if you still have weight to lose.
You can lose around 10 lbs by doing this. It never effects me because I can get a bloat of 15 lbs in a day.