Hey Deidre,
The following is based off a day before weigh in (example: Friday weigh-in, Saturday fight)
I recommend that you "cut" to the official fight weight. The "cut" should be a max of 8-10% above official fight weight. So a 70kg fighter should cut from a max of 77k.
This 77kg is a fully hydrated, fully carved up fresh fighter. If the weigh in is Friday then the fighter is 77kg waking up on the Monday after they've been to the bathroom.
There is one study on water loading by Reid Reale showing it to be an effective means of dropping more weight with no negative consequences.
I hope this helps