Has it ever worked?

Whether an effect has ever worked or not is a big factor in getting it running. If the thing was a commercial pedal, or a homebuilt that once worked fine, then there's likely to be only one or two things wrong with it. If it's a new homebuilt effect that has never worked, it's entirely possible that there are two, three, or many defects to remove.

Debugging proceeds differently if you're trying to find one needle in a haystack than if you are trying to remove a handful of needles from an haystack.

If it has never worked, you need to proceed with the section on getting newly built effects running.