DENIM DO'S
Machine wash and dry as infrequently as possible to increase the lifespan of your denim, reduce water usage and minimize energy use/carbon impact
Extend the time between washes by spot cleaning. Use a washcloth or toothbrush with a mild bar soap or a small amount of non-chlorine detergent.
When machine washing, wash on cold. This is especially true for denim with stretch (elastane, spandex, lycra) because heat breaks down elastane.
Wash with a mild non-chlorine based detergent. There are brand like The Laundress, that sell denim specific washing solutions which both gently clean and soften your denim.
Dry on a drying rack vs. the dryer to prevent shrinking and fiber break down while preserving color.
If you get a hole in your denim patching and Sashiko mending are beautiful ways to preserve your denim garment.