If you have a standard car its just a case of making sure all your fluid/oil levels are topped up and take a litre of oil/coolant/brake fluid if you have them. Check your pads have plenty of meat on them and check your tyres for any damage before you set off, also check your treads and make sure pressures are all the same. If you havnt checked for ages you may have 1 wheel at 27psi and the opposite at 37psi which will catch you out on track. Its 35psi on standard wheels/tyres nissan spec so i would start out at 33 all around then come in after a few laps when warmed up and adjust accordingly if needed. Different size wheels and tyres may need other pressures, check if needed. Again take a tyre inflator and pressure gauge with you. Always best to take a proper jack and wheel/torque wrench with you in case you come off or need to inspect underneath etc but there will be plenty of others that will help with assistance or tools if required. Finally, its best to have a warm up lap and cool down lap at around 50-70% to A- get engine, brakes and tyres upto temp and B- help everything cool down before coming off track.
And enjoy yourself.