You should water your pothos plants every 1 to 2 weeks.
A good indication of your pothos plant needing water is when the foliage begins to wilt.
It is best to water just as the pothos plant begins to wilt (not after it has collapsed), and always be sure to feel the soil in addition to visually monitoring the plant.
Water your Pothos every 1-2 weeks, allowing soil to dry out between watering.
Expect to water more often in brighter light and less often in lower light.
Some signs of over watering include yellowing leaves and black stems, while under watered plants will wilt and their potting mix will dry out.