word of advice... after the weigh ins dont eat a chicken tikka roll... as thats what i did.. and i puked after my first fight which was just before my second, and i puked after the second aswell... i won them both.. but i puked none the less lol
Try and get a copy of 'The Grapplers Guide to Nutrition'. Very good book, and talks about on the day weighs and day before.
I followed it for my first semi-pro fight going form 74kg to 70kg and it worked well. Also know a lot of other fighters who have followd it, or something very similar.
im lucky i go from 100kg to 90 kg in 2 weeks just from training hard,but i can shit 6lb aswell