Turn off the gas lines to your home. There is a main valve outside at the meter. Turning the gas supply off to the home may save you from an explosion.
Shut off the electrical power at the main panel. This can avoid shock during the disaster or damage to your electronic equipment and appliances when power is restored to an area.
Be very careful when reentering a flood or fire damaged home. These can and will collapse without warning possibly leaving whoever is in the building in the same condition as the Wicked Witch in Oz after the house fell on her. By the way, we all know you will want back into the home after a disaster, but it is really not a good idea until cleared by a professional.
The drinking water system may be contaminated. Disease can be flushed into the drinking water supply. Flood waters can be contaminated by sewage system overflows. Even a small open cut can be the start of a serious illness or infection when in contact with flood waters.
Do not turn on the electricity or gas in a damaged home until the home is checked by a professional. Damaged appliances can be a risk of fire, injury or explosion. If appliance and other basic equipment are not properly dried and cleaned before they are tuned on, you may cause permanent damage to them.