What actually worked to get a toddler sleeping through the night?

Consistency in the routine tends to matter more than any specific method. What helps most families: a predictable sequence of the same few steps in the same order, starting the wind-down before the child is overtired, keeping the room dark and cool, and putting them down drowsy rather than fully asleep so they learn to settle. Night wakings are developmentally normal well into toddlerhood, so 'sleeping through' is a moving target. If the child snores loudly, breathes through the mouth or is unrefreshed, that is worth raising with the paediatrician rather than treating as a behaviour issue.