1. Observe and protect
Note what's visible, stop further damage if it's safe to do so without special equipment, and gather whatever history you have on the house or past leaks.
2. Evaluate the house and site
A stain on drywall is the end result, not the diagnosis — the evaluation has to trace it back through the wall assembly to whatever's actually letting water or humidity in.
3. Define a written scope
Get prep work, protection of the rest of the house, materials, access logistics, permits, testing, cleanup, finish work, exclusions, and how changes get priced all down on paper.
4. Compare providers
Look past the bottom-line number to how each provider explains their diagnosis and where their scope stops — and confirm credentials independently.
5. Inspect closeout
Before signing off, confirm the post-work testing results, that cleanup is thorough, documentation is handed over, and you understand the warranty and any upkeep that's now on you.