Floodwaters can affect a home in three ways: Water damages the materials, mud and other contaminants create health hazards, and dampness promotes the growth of mold and mildew. Some simple steps (followed in order) may help reduce the effect of all three situations, according to FEMA and the American Red Cross.

Lower the humidity: Reducing the humidity can help everything dry more quickly. Open the doors and windows, open cabinets and closets, use fans to move the air (do not use your home's central air conditioning or furnace), use dehumidifiers, use desiccants (moisture-absorbing materials). You also may consider calling a professional that specializes in drying out flooded buildings to help you. Be patient, as the entire process could take a few weeks.
Sort contents and discard debris: Divide your home's content into three categories: items you want to save (move these to a safe, dry place), items to be discarded (put them outside to dry), and garbage (throw out the garbage in plastic garbage bags). Typically, there will be frequent garbage pickups after a flood.
Drain the ceilings and walls: Drain ceilings by poking a hole with a long poker and drain walls by puncturing them with an awl or knife, about 2 inches about the floor. If water drips out, cut a larger hole to allow more water to flow.
Dry the ceilings and walls: FEMA and the American Red Cross say that if floodwaters soaked the wallboard at least 4 feet above the floor, all the wallboards should be removed and replaced. If it was less than 4 feet deep, they say you can remove the lower 4 feet of wallboard and replace it with 4-foot by 8-foot wallboard sheets laid on their side. Plaster and paneling may be able to be saved if properly ventilated and dried. Cut holes in the walls low enough that they can be covered by baseboards when they're dry. (Cut both sides of interior walls, and only on the inside of exterior walls.) If there's insulation, plaster and wallboard must be removed to take out all the insulation.
Dry the floors. Most floor coverings should be thrown away, due to the mud and dirt left by floodwaters. Air needs to circulate below the floor to dry it, so remove any plastic sheets or insulation from beneath the flooring until it's dry. If the crawl space is flooded, pump it out.

If you have flood insurance, FEMA says you should retain samples of items such as carpets, wallpaper and drapes, to help the adjuster. You should also set any damaged items aside so the adjuster can look at them. FEMA warns that you should take photographs of and then immediately throw away any items that pose a health risk, such as perishable food items.

It may take some time before a repair professional can come to your home and fix any utility issues you might have. If that's the case, do as much cleaning as possible while you wait for your utilities to be restored.