To have proper control of your bike you will need a proper tire pressure. People who ride bikes are aware of the importance of the tire pressure.
If you have high pressure in your tire the bike will jump higher and you will have less contact with the ground and the bike would be uncontrollable. And if the pressure is too low then you can be in the danger of getting flats on the tire and the tire can be uncontrollable and unpredictable.
The proper pressure will differ from person to person and the set up of tire. The trail or the terrain you are riding also depends on the tire pressure.
The method of tire pressure will be all trial and error method and you will need to check the set up in normal conditions and you will need to get the best reliable pressure gauge or pump.
The starting point can be higher pressure of around 40-50 psi. If you own a tire which is without tubes then you can start lower at 30-40 psi. If your weight and of the bike is heavier then you should start with the high pressure. Try these and find out how it fares and then slowly lower the pressure. And compare the two pressures and get the right one for your bike. If you still feel the bike is not proper you can drop pressure by another 00.05psi
The checking can go as far as the tire does not go flat. But with the tubeless tire the pressure can run very low and there is no worry about the flat tires.
Once you know which setting is comfortable you will learn your comfortable pressure for the tires and you can be on your way to a comfortable biking.