eat your normal diet, just don't over do it, and try to stay away from the "heavy" foods (stuff you feel dragging you down the next day). Hydrate the night before - you'll want to limit fluids before weighing in the next day.
I think making sure you have plenty of energy in reserve, get a good night's sleep, and feel good are more important than anything else. You can also ask your coach.
I'd stay away from anything you're not familiar with as you might find out the hard way that you're sensitive to a particular type of food, etc.
The other major consideration is how nervous does your stomach get before a competition. If you get a nervous stomach, you'll want to eat frequent, small meals throughout the day, and those meals should be relatively bland (boiled chicken, rice, etc) - keep something in the tank, but don't irritate the tank.
Pre- weigh yourself in the morning; it'll give you a better idea of what you can/should eat in the morning. If you're right on the edge first thing in the morning, take the porridge to go, but get some easy sugar in your system - a tablespoon or so of honey so you have fuel without too much actual weight.
And, before you get too far into the diet thing, make sure the tournament actually has a habit of dividing into Olympic weights in your division. Talk with your sensei or instructors, check last year's rosters/brackets and make sure you're not subjecting yourself to unnecessary diet (for example - very few women's divisions in my neck of the woods break into Olympic weights, even for the bb division. Usually, it's just light and not so light with the dividing line between the two set by who actually shows up to play. Dieting to "make weight" is therefor a silly distraction)
Above all, have fun this weekend.