To clean a mattress effectively, follow these steps:

1. Strip all bedding and wash sheets, pillowcases, and blankets in hot water to kill dust mites and germs.
2. Vacuum the entire mattress surface with an upholstery attachment to remove dust, hair, and debris, focusing on seams and crevices.
3. Spot-clean stains with a mild detergent solution or a suitable stain remover (enzyme cleaner is good for biological stains). Use a clean cloth to blot stains gently, avoiding soaking the mattress.
4. Apply a thin layer of baking soda over the mattress and leave it for several hours to absorb moisture and odors.
5. Vacuum up the baking soda thoroughly.
6. If the mattress is flippable, repeat the cleaning process on the other side.
7. Air out the mattress by opening windows or placing it in sunlight if possible to help it dry and refresh.

Avoid harsh chemicals like bleach, and always test cleaners on a small area first. Using a mattress protector helps keep the mattress cleaner longer and reduces cleaning frequency. This comprehensive approach keeps mattresses hygienic, fresh-smelling, and extends their lifespan.