There are two settings that have the greatest effect on sound quality:
This is how sensitivity the microphone pick up is and this is adjusted on the microphone/body pack itself. Typically for general speaking the sensitivity should be set around -15 to -18 dB. You will need to adjust this depending on the exact application. Adjusting closer to 0 dB is will be more sensitive and further away from 0 dB is less sensitive. If the microphone is too sensitive the input will overload the microphone and the AF level will peak and the audio will be clipped. It is suitable to adjust the level so that the AF peak indicator lights up only briefly during the loudest passages.
This is how strong the signal is exiting out of the receiver into the sound board/speakers/etc. Typically this will be set to 0 dB or +6 dB if connected to equipment which is expecting a line level input . If you are connected to equipment expecting a mic level input you will typically need to drop this AF output down to -24 dB or -30 dB. If your equipment has the option, it is best to try to run the equipment in line level mode.
NOTE: If the AF Output is too high it may over load the input on any connected equipment (sound board/speakers/etc) and may create noise in the form of distortion/rumbling.