Dracaena trifasciata
Snake plants store water in thick leaves and thrive on neglect. The most common way to lose one is to water it too often, especially in a dim room or in winter.
Short answer: for a snake plant, with the starting settings below (a 6 inch pot with a drainage hole), check the soil about every 12 to 18 days in spring and summer and every 18 to 27 days in winter, and water when the top two inches of soil are dry. Give it a full drink until water runs out the bottom.
Your answer
Water when the soil reaches this point
How it shifts through the year
Water slowly until water runs out the drainage holes, then empty the saucer within an hour. The right amount depends on pot size, so go by drainage and how dry the soil is, not a fixed measure. Give a full soak, then wait until the soil is dry before watering again, since small frequent sips lead to rot.
Often much less than people expect, sometimes every two to four weeks, and less in winter or low light. Check that the soil is dry first.
Rot from overwatering is the usual cause. Remove the plant from the pot, cut away soft roots, and repot in fresh dry mix.
Tools that help
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Related guides
Estimates use rules of thumb. Always confirm with your finger: push it about an inch into the soil before you water.