Yeah, 3/4 tank and upward. I personally know the results of 1/2 a tank and less and it isn't all that fun.
In short, I don't think tyre pressures would be too important tomorrow. Not only coz it's all a bit of fun, but also because it will be quite a hot day and so I would imagine the pressure would naturally go up a few PSI due to the heat of the day and the soak in the track surface. Having said that, going up a couple of PSI from your road-going pressures is generally recommended when doing motorsport.
It's all personal preference, but as a guide, 36-40psi. Higher at the rear should result in a little more slide
e.g. 36 F, 38 R.
Otherwise you don't need anything special.