1. Document first, diagnose second
Record what's visible, take reasonable steps to stop it from getting worse, and pull together whatever history exists on the home.
2. Evaluate the house and site
Install method, flashing approach, sill condition, frame material, glazing package, trim restoration, and sun exposure on that wall count for as much as the product itself.
3. Put the scope in writing
Cover preparation, protective measures, materials, site access, permitting, testing, cleanup, finish restoration, exclusions, and how change orders are handled.
4. Stack the proposals against each other
Confirm credentials, then look at how each provider justifies their approach and where their responsibility ends — that matters more than the total at the bottom.
5. Confirm closeout before moving on
Make sure testing happened, the site got cleaned up, documentation was handed over, warranty terms are clear, and you know what upkeep falls to you afterward.