So this week AF is due, and I'm so nerous about gaining weight.

I have gained before while dieting and AF visiting and I have lost before while dieting and her visit, so is there anything I can do to insure no weight gain? Extra water? Stay away from Salt? ANYTHING??? My goal is to be somewhere in the mid 170's by March 28th, my grandparents 60th wedding anniversary and I will be seeing tons of family I havent seen since I was a kid and I really want to look decent by then. Any help would be great!!!!