The following is a quick video on how to clean a 5 gallon Corny keg.
To clean a keg you will need the following items:
1) PBW (Powdered Brewery Wash) or similar food grade cleaning agent
2) A scrubbing sponge or brush
3) A socket wrench or crescent wrench to move the body connects
4) Warm or hot water
5) A sanitizing agent such as Star San if you wish to sanitize the keg at the same time
Food grade cleaning and sanitization chemicals can be purchased here: