While laundering seems like a simple task, a few methods help preserve the lives of dark-colored laundry items. Dark colors should be washed on their own to prevent bleeding onto other colors. To reduce friction on clothing and allow detergents to fully dissolve, do not overload the washer.
After removing any delicate or hand-wash items, sort your laundry according to color. Dark colors go in one pile, and whites or items that can be bleached go in another. Dark-colored clothes should be turned inside out before the wash to help reduce fading. Check the care instructions and separate items according to washing instructions. Take time to sort dark laundry by fabric weight as well; it will reduce friction during the wash cycle and help reduce fading.
Black jeans require special handling to keep them looking dark. Empty all the pockets and turn the jeans inside out. It's best to wash jeans on their own to avoid overcrowding the washer. Always wash black jeans in cold water and on a light or delicate cycle. Wash as seldom as possible and air-dry dark jeans rather than use a heated, tumble dry.
If you use powdered detergent, dissolve the detergent in cold water prior to adding clothes to the machine; liquid detergents work best for dark colors. Do not use chlorine bleach with dark clothes and even color-safe bleach can cause fading. One trick is to add a cup of vinegar to the wash to help preserve the color. Use the shortest, lightest wash cycle possible to reduce friction in the wash.
Keep the load size small and make sure there is plenty of water for the clothes to move around in. You may try just soaking dark clothes and skip the agitation cycle entirely, then finish with a rinse and spin. If at all possible, air-dry dark clothing on a clothesline or drying rack but avoid exposure to the sun. If you don't have a line available, use the lowest heat setting on the clothes dryer. The heat can cause more fading than the tumbling.