Some ways to kill spider mites include insect sprays that are specifically made for mites and oils, such as neem oil. Diluting neem oil with water and spraying it on the plants is a common and safe way to get rid of spider mites that does not harm anything else.
Spider mites enjoy dry places, so spraying the plants with water often also deters them. It is important not to overuse chemical insect sprays because they can kill the other insects that prey on spider mites, such as lady bugs. The death of beneficial insects leads to an increase in spider mites.