Hot water and Soap
Fill the pan with water and add dish soap to create bubbles. Bring the pan to a boil on high heat for 10 minutes, stirring occasionally. Then Drain the soapy water from the pot and fill halfway with cool tap water but no soap or detergent of any kind. Bring this mixture up to a rolling boil again while stirring constantly for 5 minutes before draining out all of the liquid completely (this removes any stubborn residue).
Wash the pot once more in hot soapy water, rinse thoroughly, dry over low heat, then coat lightly with cooking oil.
Salt is one of the best cleaning solutions that has never failed to help cooks in any case. Fill your cookware with warm water and a handful of salt. Allow it to rest for at least 20 to 30 minutes, then use a few drops of detergent and a soft sponge to finish the job.
You may boil the water and clean the pan after it has completely cooled if you need to remove persistent stains.