Check the roof and attic for signs of leaking. Did ice dams push the gutter away from the roof? Is the water leak coming from around vents, pipes or the chimney? Inspect the ceilings on each floor for water stains. Look at all the areas that have plumbing, including the bathrooms, kitchen, hot water heater and washing machine. Are there signs of a leak with the plumbing? Inspect the floor and walls in the basement for signs of water coming in through the foundation. Repair any issues to keep water damage from continuing.
The first two days after a water leak is critical. Some items can be dried and cleaned before mold or fungal growth can grow. In general, drywall, ceiling tiles, papers, laminate furniture and particle-board furniture will need to be discarded before the 48-hour time frame. The portions of the wet drywall need to be removed, plus an additional 12 inches above the wet portion. Papers can be photocopied before being discarded. Only in the most minor of water leaks or steam leaks can ceiling tiles, laminate wood and particle-board items be dried, cleaned and repaired.
Carpet saturated with sewage should be discarded immediately. Don't forget the carpet that runs under cabinets. Carpet that is saturated with water might be able to be salvaged. Remove cabinets and furniture from the room. Use a wet/dry vacuum to remove as much of the water from the carpet as possible. Shampoo the carpet. Make a bleach and water solution that is one part bleach to 10 parts water. Test the solution in an inconspicuous area first. Another option is a biocide to kill the bacteria. It will not kill fungus. If this is not an option because of the chemical, you can hire a commercial steam cleaning service to clean the carpet. Do not replace the furniture and cabinets until the carpet is completely dry. Fans and dehumidifiers can speed the drying process.
Hard surfaces can be cleaned with a mild detergent followed by a rinse of the bleach-and-water solution used for carpeting. Do not rinse the bleach. It needs to stay there to kill the bacteria and fungi. On metal surfaces, just use the detergent because bleach corrodes metal. Do not use bleach in an unventilated area because of the fumes it emits. If the electrical system was saturated, turn off the power to the damaged areas. An electrician needs to inspect all wiring, light fixtures and outlets. Any item with an electric motor and any electronics should be sent to a repair shop to be opened, dried and tested for damage. If the HVAC system was part of the water damage, do not run the system until it can be professionally cleaned.