1. Triage and protect
Stop active water, protect what’s nearby, and figure out whether this can wait until morning or needs someone now.
2. Diagnose
Look at how the fixture behaves, what the pressure’s doing, how it drains and vents, what the pipe is made of, and what’s been touched before.
3. Define the scope
Put in writing exactly what’s being repaired, how it’ll be accessed, who patches the finish, what’s permitted, how it’s tested, and what’s excluded.
4. Complete and test
Finished work should be supported properly, reachable where it matters, and tested under real conditions — not just eyeballed — before anyone calls it done.