1. Make sure that your heater and defogger fan work - people in the Northwest are less likely to run cage tubes through that space than people in Texas.
2. Make sure that holes in the floor are plugged - I got a geyser of steam up my pant leg in the passenger seat of a car that didn't have the OE rubber/plastic plug in a 2" hole in the floor, after water hit a hot exhaust pipe. Needless to say, it really steamed up the windows, too.
3. Don't panic if it's wet - rain tires aren't really an issue until there is real standing water on the track (when you can't see the texture of the aggregate poking up through the mirror finish of the water.
4. Come prepared to block off your radiator and/or oil cooler to get temps up to the correct point - oil particularly shouldn't be below 210-220* to boil out water.
5. If you can adjust your roll stiffness, try runnning it as soft as you can - don't make huge balance changes to do this, however, like just disconnecting the bar on one end.
6. Make sure that you perpare so that you don't suffer OUT of the car - good awning, warm place to hide, extra socks, gloves, maybe some rubber overboots for the driving shoes...
7. Go into the experience expecting it to be fun - crappy weather is easier on drivers and equipment and can be VERY educational if you don't assume that it will be hell.
K