Start
here, and turn to page 60 for flat settings (read the text on page 61 for a correct description of the photographs, as they are mislabeled).
You won't stay with flat, but it will help you hear what you're missing, what's too much, and you can adjust from that point. What's good will change with preference, style, etc, and even if those are stable, with the room and speaker placement in the room, where adjusting the lower end of the spectrum is often necessary. Don't be afraid to cut bass if it sounds better to do so!
