How do I know when to water?
Answer: If you are container gardening, then you would water the plant really well and weigh the plant (container and all, please do not pull up bare rooted plant because it will cause unnecessary trauma to the plants). When it losses around 25% of it's weight you want to water again. You and 10 of your friends can have identical setups with the same plants and most of you would need to water at different cycles. The larger and healthier the plant the more water it will need. Climate, humidifiers, dehumidifiers, and air circulation all play a big part in how often to water.
Soil/Hydroponic Growing Medium shown here is too dry.