Don't get too hung up on being over prepared for your first one - just have fun. Is it a novice/sessioned day?
Get decent fluid in the brake system, decent pads too.
Check fluids/tyres/brakes/wheelbolts before, during and after once cool
If you feel/smell/hear/see anything unusual, come in straight away.
Build up slowly and leave yourself an exit plan. Being up the chuff of some French clutter is really fun, but if he does something unexpected, you might end up off.
Do a cool down lap, roll around the paddock too if you feel the need. Leave it in gear, no handbrake.
Most importantly - get a lesson.