1. Steam Cleaning: To remove stains, put some water in a pot or pan and boil it. The steam from the boiling water will help soften the stains and dissolve the residue stuck to the surface of the pot or pan. Then scrub the stains with a spatula or a soft sponge.

2. Vinegar and Bicarbonate Mixture: Put equal amounts of vinegar and baking soda in a bowl. Apply this mixture on the stains and leave it for a while. Then, scrub the stains using a soft sponge or cloth. The chemical reaction of vinegar and baking soda will help remove the stains.

3. Lemon and Salt: Take half of a lemon and sprinkle some salt on it. Apply the lemon slice on the stains and rub it. The acidic properties of the lemon and the abrasive effect of the salt will help to remove the stains.

4. Dish Soap and Hot Water: Fill the pot or pan with hot water and dish soap. After waiting for a while, scrub the stains with a soft sponge or brush. Then rinse.

5. Cut Potatoes and Salt: Pour some salt into a pot or pan and place the cut potato slices on it. Place the pot or pan on the stove and rub the potato slices with the salt. Then let the pot or pan cool, most of the stains will be dissolved.

Any of these methods can help remove stubborn stains, but depending on the material and coating type of your pots or pans, some methods may be more effective than others.