Modern bike, modern tyres, normal body weight -4psi rear - 5.5 psi front.
Drop rear for very soft and muddy going or if riding easier routes.
Check pressures if change in temps - ie cold night - sunny morning. Tyres can gain 1 psi easily in theses conditiions. Don't park bike in the sun before checking - black tyres absorb a lot of heat energy if left in the sun.