To clean a dirty mattress, the key steps include stripping the bedding and washing it separately, vacuuming the mattress thoroughly, spot-cleaning stains carefully with gentle cleaning solutions, applying baking soda to absorb odors and moisture, then vacuuming again. It's important to use minimal liquid and avoid soaking the mattress. Detailed steps:

1. Remove all bedding and wash sheets, pillowcases, and blankets in hot water if possible.
2. Vacuum the mattress surface and sides well to remove dust and debris.
3. Spot-clean stains with a mild detergent or enzyme cleaner applied on a cloth, blot gently (avoid soaking), and rinse spots with a water-dampened cloth.
4. After stains dry, sprinkle baking soda evenly over the mattress surface. Let it sit for a few hours to absorb odors and moisture.
5. Vacuum up the baking soda thoroughly.
6. Flip the mattress and repeat vacuuming and baking soda application if the mattress design allows.
7. Let the mattress fully dry before making the bed again.

For specific stains like blood or urine, enzyme cleaners or diluted hydrogen peroxide (3%) may work well, applied carefully to avoid damage. Steam cleaning and using a warm iron over a damp cloth can also help disinfect but should be used cautiously depending on mattress type. Using microfibre cloths and gentle soaps ensure the mattress fabric isn't damaged during cleaning. Regular cleaning and airing out prevent buildup of dust mites and odors.