Water can be one of the most destructive forces of nature. Every year flooding destroys millions of dollars in property and claims numerous lives. Flooding is the most frequent occurring natural disaster worldwide. It is nearly unstoppable by any means. Preparing for the eventuality of flooding is a nessecity for all. 

Make sure you have a Bug Out Bag ready. See the article on it for practical advice.
Make sure you have evacuation routes marked on a paper map. 
Make a list of the contents of your home & get copies of your insurance documents in your bug out bag.
Assess your flood risk. Go to fema.gov to see flood plains in your area and plan accordingly. 
Make sure you have a family emergency contact plan in place.

If told to evacuate, DO IT, don't wait. Don't forget your bug out bag.
Make sure to tell someone where you are going when evacuating.
Remember natural disasters are breeding grounds for looting. Secure your home.
Mass evacuations are chaotic events and bring the worst out in people. Plan accordingly.
Listen to the radio for alerts.

Avoid walking or driving through flood waters.
Just 6 inches of moving water can knock you down, and 2 feet of water can sweep your vehicle away.

If forced to move through floodwaters watch out for debris and deeps spots. Use a long stick to check water depth in front of you. 
In urban areas remember if there is flooding then sewers have also flooded and sewage is in the water. Avoid going in the water if possible and DO NOT drink water that has not been filtered and purified. 
If there is a chance of flash flooding, move immediately to higher ground. Flash floods are the #1 cause of weather-related deaths in the US. 
If floodwaters rise around your car but the water is not moving, abandon the car and move to higher ground. Do not leave the car and enter moving water.
Avoid camping or parking along streams, rivers, and creeks during heavy rainfall. These areas can flood quickly and with little warning.