First, learn how to clean your washing machine top loader and stick to a schedule. That alone will keep it running smoothly, remove buildup before it happens, and prevent any mold or mildew growth. Always use the right amount of detergent and limit or avoid the use of fabric softeners. I know it makes laundry smell delicious, but it's the number one cause of buildup on machines and clothing! Know if you have a standard or HE washer, then measure out the appropriate amount according to your detergent container. A little really goes a long way.