You'd be hard-pressed to find among a small group of writers one or two who don't meditate. It seems to be more popular among creative types than among ascetics these days. Which begs the question: Why?
As a long-time advocate for meditation, I have a few opinions on the matter.
For starters, writing, painting, or any other creative act, requires a certain mental state. You need to be simultaneously focused on the task at hand, but also somehow mentally absent from the act to a degree that allows an openness for newer, better ideas to pervade that particular time and place. Meditation allows that balance between clarity (i.e., not a cluster of loud and distracting thoughts and ideas) and that open absence from fixating on the creative act (you don't ride a bike by consciously telling your left and right legs to pedal, do you?)
Then there is the matter of self-consciousness. Not in the sense of being aware of what you are doing. Rather, the sense of being worried about what you are doing. In sports, this is referred to ask "choking." Meditation helps push that worrisome sense the corners of the mind, making writing and other endeavors less stressful with regard to how our works will be judged by others.
I hope anyone reading this who hasn't tried meditation for better creative results will try it. You don't need to be a bald-headed monk on a mountaintop to sit still and be quiet. You don't need to be chasing enlightenment to benefit from stillness.