Put an extra quart of oil in the car. Maybe even a full quart if it's a 5+ quart capacity. More oil in the pan reduces the likelihood of a starved oil pickup.

Definitely learn the seatbelt trick. Next best thing to having a harness, and it's free.

And I'll second "don't worry about the tires". If they started out brand new, they'll be broken in after about 2 laps. Do make note of your cold tire temps and how they translate to hot temps. Check for sidewall rollover after your first shared_session. Add pressure if necessary. Otherwise, by about your third session, you should be starting to get a feel for whether the car has significant over or understeer issues and you can tweak the tire pressures a little bit. In general, though... for a first time track event, set the pressures a little on the high side and just plain don't worry about them.