word.....my rule of thumb for any street tire is not to get over 40 psi as your hot endpoint.track conditions are much more consistent in raising pressures, than public roads, but I'm sure some of our aggressive canyon carvers can generate some heat
Another rule of thumb to use to adjust tire pressures throughout the track day absent a pyrometer is to use the butt dyno.
If the car feels really good at the beginning of a session and is seriously going off toward the end, you probably started too high and are crowning the tread toward the end of the session as they got hot. You might want to try 2-3 PSI lower next session (depending of course on heat of the day, etc.) Of course it could also mean you started way too low and got the tread overheated, but let's assume you're starting pretty close based on the advice you've already received here.
If the car feels a little squirmy at first but gets pretty good three-five laps in, and stays OK most of the session, you're in the ballpark and shouldn't need to adjust more than 1-2 PSI.
You can dial in either end of the car using this method; front might be good but if the car gets tail-happy toward the end of the session, might be overheating the rears. Vice-versa for the fronts.
If the car never does feel right, you probably started too low. You can also feel and hear this and depending on the tire can see it by looking at the shoulder when you come off the track. If you're wearing all the way over the edge of the tread onto the sidewall you might need more air, but this method is not terribly accurate as it depends on the characteristics of the particular brand, model, and size of the tire (and its wheel width), and also on camber settings.
These methods are inherently and terrible imprecise but failing all else, try the butt dyno as another data point.