Roof leak repair
The stain on a ceiling is where water finally came through drywall. The place it entered the roof is somewhere above it, and frequently several feet away.
Water travels before it drips
Once water gets past the shingle it runs down the underlayment, along a rafter, or across the top of the ceiling until something interrupts it — a light box, a seam, a nail. That is where it appears. Tracing a leak means starting at the stain and working uphill, usually from inside the attic on a wet day.
Where they usually start
Step flashing where a roof meets a wall, particularly along an attached garage. Chimney flashing and the counter-flashing set into the mortar. Around skylights. At plumbing vent boots, where the rubber collar cracks after fifteen or twenty years of sun. In valleys, where debris holds water. And at the eaves, where ice damming pushes water backwards under the shingle — a seasonal problem across the whole region.
The field of the shingle is rarely the culprit unless the roof is genuinely at the end of its life or something struck it.
Before anyone gets on the roof
Put something under the drip and move what is below it. Photograph the stain and the attic side if you can reach it safely, with the date — it matters for a claim. If the ceiling is sagging or bulging, stay out from under it; saturated drywall lets go all at once. And nobody should be walking a wet or iced roof to look for the source.