The "correct" way involves being a bit of an audiophile and knowing what to listen for. You professed at the top of the thread that you aren't an audiophile.

Basically, you move the sliders to remove frequencies that are too prevalent in the spectrum. You just fiddle with them, a little at a time, and try to listen to what effect they have on the overall sound of the music in your car. Adjust them to where each band sounds the most pleasing to your ear.