Unplug the microwave
Remove the turntable and roller ring
Wash the turntable and roller ring with warm, soapy water
Wipe the interior with a damp cloth
Fill a microwave-safe bowl with water and a few slices of lemon or a splash of vinegar
Heat the bowl for 3 to 5 minutes
Let the steam sit for a few minutes
Carefully remove the bowl
Wipe the softened grime from the interior
Clean the door, handle, and control panel with a damp cloth
Dry all surfaces with a clean towel
Reassemble the turntable and roller ring
Plug the microwave back in