Tire load rating
I've got Load Rating E tires on both my trucks - so max pressure is 80psi. Around town, I'm usually sitting at 55-60psi for a softer ride, but on the highway I'll do 60-65psi. When I'm towing or hauling a heavy load, I'll go to 70psi or more, depending on what the flex in the sidewall is telling me about my load.
My car tires max pressure is 42 or 45, so I sit them at 38-40 most of the time so the car doesn't lean too much around corners.
Each person will have a different feel, I'm sure, but ... for the most part I sit closer to the higher pressures, myself.