Setting audio levels: loud enough, never distorted

Aim for consistent levels, with peaks in the green or amber and never hitting red. Distortion can't be fixed afterwards.
Match levels between presenters, guests, music and adverts, so listeners don't keep reaching for the volume.
Many broadcasters measure overall loudness with the EBU R128 standard: produced programmes are aimed at −23 LUFS, with true peaks no higher than −1 dBTP. Online streams are sometimes delivered louder (typically between −20 and −16 LUFS). Your station's processing settings decide what goes out, so follow engineering's guidance.
Leave the on-air processor settings alone. If the station sounds wrong, report it with the time and an example.