When all standing water and debris have been removed, it's on to phase 2: cleaning and disinfecting. First, mix up a solution of cleaner in a large bucket. Any kind of general-purpose household cleaner will work.
Be sure to follow dilution instructions on the cleaner. Mop all hard-surface floors and wipe down all walls. Start at the top and work down. Let everything dry, dump the cleaning solution, and mix up a 1:10 solution of household bleach and water. Go over everything again. Have another bucket nearby for each step, and rinse your cleaning utensils often.
If there's hard-to-remove silt and dirt on concrete or masonry foundation walls, you might have to use a high-pressure hose or power washer to get it off. First, try scrubbing them with household detergent and a stiff-bristled brush. If they refuse to budge, call in the power washer.
More on Walls
In the Nick of Time
Water can also get trapped in wall cavities. If you think there's water trapped behind your walls, but you're not sure, take the baseboard off (if there is one), and tap a sharp object through the wallboard. Aim your tap about four inches or so off the floor. If water drips or pours out, make a bigger hole so water can drain out.
As you're working on the walls, you might notice some that appear to be weeping water. This means that the wallboard is soaked. If you leave it in place, it will eventually dry out. However, doing so can allow mold growth. If you're dealing with black water from a sewer problem, you're also facing contamination problems.
A better approach is to strip off the wallboard or paneling to a point above where the high water mark was. This will also help dry out wet wood and insulation.
If there's fiberglass batt insulation behind those walls, and it's muddy or contaminated, you should discard it. If it's just wet, it will dry out but it will take a long time. Cellulose insulation, which can lose some of its protective qualities when water-damaged, should also be removed and replaced.
If there are vinyl wall coverings on any affected walls, and water damage isn't too severe, see if you can pull the wallpaper up past the watermark. It's probably loose on the bottom from getting wet, so this should be pretty easy. If you can get it up, tape or otherwise anchor it in place and let it dry out, then clean and reapply it after everything is dry.
If the walls are soaked, pull this stuff completely off. Not only does it keep underlying wallboard from drying properly, the glue used to adhere it is a breeding ground for mold and mildew.
Walls with water-damage stains can be repaired and repainted. Wood surfaces, such as trim, doors, or paneling, can usually be refinished or repainted. For more information on how to do this, see Repairing Water-Damaged Interiors. Walls with extensive water damage might need to be replaced. It's typically best to hire a contractor to assess the damage and estimate repair costs.