You should rinse dentures after eating to remove food debris and brush them at least once per day. Remove the dentures before brushing and clean them using a soft-bristled brush and gentle denture cleanser, such as Polident. Brush your natural teeth, if you have them, and use a soft toothbrush or gauze to clean your cheeks, palate, and tongue.
In addition, you should soak the dentures overnight in water, white vinegar, or a store-bought denture-soaking solution to remove debris and ensure they maintain their shape. Some of these solutions have harmful chemicals, so it's important to thoroughly rise the dentures before putting them back in your mouth in the morning.
You can also add lemon juice to water to help with stain removal, but dentures shouldn't soak for more than 40 minutes. Alternatively, you can gently brush the dentures, while out of your mouth, with hydrogen peroxide to remove stains.