When bad weather strikes you need to act quickly. A flashlight and a storm radio are two very important items to have on hand. If a tornado is approaching find a safe room in your basement with no windows. If you have your storm radio with you then you will know when the warnings have passed your area. Tornados, hurricanes, hail and damaging straight-line winds can destroy a house in seconds.
The National Weather Service issues warnings. http://www.nws.noaa.gov/
Only when a storm has safely passed can you go out to assess any damage. A tree that has fallen on your house is pretty easy to assess, but remember hail and straight-line winds can damage a homes structure and a professional contractor should be called to find out if you have any damage to your roof and siding. These guys know what to look for and are helpful when you need to file a claim and work with your insurance company.