Properly drying and curing your marijuana is extremely important. I know a lot of growers that put in a lot of time, effort, and thought into the vegetation stage and budding stage. Yet many of these same growers drop the ball when it comes to drying and curing their marijuana, resulting in sub-par to mildewy nugs. Below is a great video by the legendary grower Jorge Cervantes on how to dry and cure your marijuana properly.
Aside from needing sunlight each day and good soil to grow in, cannabis plants also need a fair amount of water.