Short Answer
First: protect people and belongings, contain water if possible, avoid electrical hazards, document the damage, identify whether active water is entering, and contact an appropriate professional for investigation.
Detailed Explanation
Discovering a ceiling leak can be stressful, but taking the right steps immediately can minimize damage and help with diagnosis. First, protect people and belongings — move furniture and electronics away from the area, place a bucket or container to catch dripping water. Avoid electrical hazards — if water is near light fixtures, switches, or outlets, turn off power to that circuit. Document the damage with photos for insurance purposes. Try to determine whether water is actively entering (is it still dripping?) or if the stain is from a past event. Then contact a professional to investigate the source — don't assume it's the roof until the source has been properly diagnosed.
Why It Matters
Taking the right immediate steps minimizes damage, protects safety, and preserves evidence for diagnosis and insurance.