on track the two gauges to look at are water temperature (all cars have them) and oil pressure (only some cars do). Failing that you will have an engine/oil warning light. Keep your eye on these.
to start with 4-5 laps of WP at a time are good........come in check things out and then head back out.
A couple of tricks re water temp.....
1. you can run your heater at full - the heater works by drawing heat from the coolant. At the very least this will slow down the over heating process, depends on the car as to how effective this is, but it does work.
2. If you are following a car/s closely this interupts the airflow into the intercooler/radiator. You will run cooler with clean air - so get around them or give them half a lap.....its surprising how quick temps can come down if you get clean air in and stay out of the throttle.
Strange. I've never seen my water temp gauge move higher than normal, and my oil temp has never gone over 90'C. Even if I sit on 7,000rpm for nearly all of a 20 minute session. Interesting that stock cars should overheat, mine's nothing like stock, I'm running an undersized radiator, a massive FMIC, two transmission coolers, air-con condensor and no oil cooler. But the tips above are good
Also, don't put your handbrake on when you're in the pits and try to keep your foot off the brake while stopped after a session. I warped my rotors nicely after doing this. Keep making sure your wheel nuts are tight and don't over-inflate your tyres.