Those that want to consider the environmental impact can go "green" with a miniature hand-operated version. They are inexpensive and use very little soap and water, and no electricity. If you want the absolute king of the hill when it comes to engineering and performance, treat yourself a Miele washing machine.
Periodically clean the interiors of the machine with water, baking soda (half cup) and white vinegar (3 cups). Run the machine without load after filling water with the above substances. All residues and deposits formed inside will be removed. If necessary consult the company representative about the preventive maintenance. In the case of new machines make use of the free maintenance service offered by the manufacturers. Remember the adage "prevention is better than cure".