Allow the soil to dry out completely between waterings, as the mother-in-law plant doesn't do well in moist, soggy soils.
Move the plant closer to a sunny window -- lack of light can lead to yellow, sickly looking plants. Move the plant to its new location gradually over time, so it can slowly adjust to its new lighting conditions.
Move the plant out of hot, direct sun if the yellowing is accompanied by burned-looking patches. Mother-in-law plants can tolerate full sun, but if they're used to shadier conditions, they may burn and yellow. Reintroduce the plant to the sunnier location slowly, giving it time to adjust.
Transfer the plant to a bigger pot if the leaves look crowded in addition to being yellow. Mother-in-law plant has strong, fast-growing roots; while they can tolerate begin overcrowded, this may involve losing some color.
Apply a balanced liquid houseplant fertilizer during your next watering if the plant has been in a container for a long time. Mother-in-law plant can live for years, even decades, and might use up all the nutrients in its container.