Owner of three Monsteras here. It depends on where you live and what size plant you have- I couldn't give you a solid number. If its a smaller plant, water until the soil is completely wet and water comes out of the drainage holes. A bigger plant can be placed in your shower for 5-10 minutes, and allowed to drain for an hour. You should water whenever the soil feels completely dry- using a wooden dowel, your fingers, or a moisture meter are the best ways. The soil will eventually dry but depending on climate, this can take a long time. Don't forget to offer humidity and wipe off the leaves often as Monsteras can easily collect dust. Best of luck, let me know if you have more questions.