Return all frequency adjustment knobs, volume adjustment sliders, gain dials and fade adjustment knobs to 0 or neutral settings.
Connect the headphones to the graphic equalizer and focus on the sounds coming through the equalizer.
Turn off all channels on the equalizer.
Turn on the channel(s) referring to the instrument you want to set.
Have someone play the instrument at the highest performance volume and gradually increase or decrease the volume slider so that the bars on the volume gauge peak at the low end of the yellow range. The mid-level of the green range is too soft and the red range implies the instrument will get cut-off in performance.
Repeat steps 3, 4 and 5 for each instrument -- including vocals.
Have people play all non-amplified instruments at the same time. Amplified instruments go straight in to the mixing board and will not interfere with each other.
Pick out each instrument sound channel individually and check if it picks up sound from instruments other than the intended instrument.
Increase the frequency knobs associated with the channel's target instrument; gradually decrease them if the channel is noticeably picking up sounds from other sources. Repeat step 5 if you have to make adjustments.
Repeat steps 8 and 9 for all instruments.
Remove the headphones, turn on all channels, and adjust the output volume to increase and decrease the volume over the speakers or PA system until you can hear the music clearly over the audience.