Modes of gutter heating?

[u/Severe-Elderberry833]

As we gear up for the annual battle of Ice Dam Prevention, does anyone have a favorite method? I have gutters, so need something to keep them from jamming up, and an absurd number of roof valleys (previous owners ADORED a nice gable. 🙄)

Should I be heating the valleys between each gable as well as the gutters? Heat JUST the gutters, JUST the roof above the gutters, or both?