Dislodge as many mites as possible using a strong stream of water. Done on a regular basis this can reduce populations dramatically. Wash the plants either outdoors or in the shower. Protect the soil so it is not washed out of the pot by the spray. Use insecticidal soap.
Many insecticidal soaps are also effective in controlling mites so check the label.
Other soap products may actually be labeled as miticidal sprays. These soaps are specially formulated to kill mites and not damage plants. They can be very effective if used frequently until the problem is under control. Insecticidal soaps are considered nontoxic to humans and pets and are very safe for use indoor or outdoors. Use superior horticultural oil sprays.