Don't start bad habits off now..... eat normally because whatever you do for your first weigh in, you'll then do it forever!
There are people on here who are pretty much nil by mouth on WI day, but there are a lot who eat normally but not huge meals, it's been discussed a fair bit in the past on here but I'm sure lots of people will offer their advice!
I have cereal for breakfast and then salad and fruit for lunch. I don't have a drink past about 2.30-3pm though. This is daft, but I've always done it, and that's what I mean about bad habits!