Never stick jeans in the dryer. Either hang them to dry outside if it’s a nice day (keeping them out of the sun), or put them on a drying rack.
Skip the soap—it fades the dye—but when it is time to give your jeans a good wash, use vinegar—it’s a natural cleaner and it also helps to lock color in and prevent any bleeding. Just soak your jeans in a bath of cold water mixed with a cup of vinegar for about an hour, then lay them flat to dry. Don’t worry, the smell of the vinegar will dissipate as they dry. If you do need to use the washing machine, set it to cold and add the vinegar into the washer.
Spot clean. When your jeans get stained, don’t throw them into the wash, just attack the spot. Use a laundry stain remover, leave it on for a few minutes, then use a damp cloth to wet the area and scrub the stain away.