For effective cleaning, unplug the waffle iron, wait several minutes, and then wipe the grid plates down with a damp paper towel while they're warm, not hot.
Place the paper towel in tongs to keep your fingertips safe from the heat. Use a toothbrush for stubborn bits, and once cooled, clean the appliance thoroughly with a soapy sponge.
For a thorough waffle iron cleaning, create a paste with baking soda and hydrogen peroxide, apply it to the iron, and allow it to sit until it absorbs the grime.
After wiping away the paste, use a toothbrush to remove any residue, then clean the maker with a soapy sponge. If applicable, remove the grid plates and soak them in warm water.
Soaking the whole appliance in water could permanently damage it. Be sure to wipe it down with a damp paper towel and a soapy sponge and pat it to dry after each use.