Flannery O'Connor gives simple but commonsense advice on the practice of making writing a habit:
"I'm a full-time believer in writing habits, pedestrian as it all may sound. You may be able to do without them if you have genius but most of us only have talent and this is simply something that has to be assisted all the time by physical and mental habits or it dries up and blows away. I see it happen all the time. Of course you have to make your habits in this conform to what you can do. I write only about two hours every day because that's all the energy I have, but I don't let anything interfere with those two hours, at the same time and the same place. This doesn't mean I produce much out of the two hours. Sometimes I work for months and have to throw everything away, but I don't think any of that was time wasted. Something goes on that makes it easier when it does come well. And the fact is if you don't sit there every day, the day it would come well, you won't be sitting there."
O'Connor also believed the habit of art -- especially the discipline of drawing -- which enabled an author to really see and observe the world. The attention to detail learned from the practice of drawing, were transferable to writing. You can read a terrific article "Flannery O'Connor and the Habit of Art" in the Paris Review which explores O'Connor's college career as a cartoonist for The Spectrum, at the Georgia State College for Women and her ideas about the relationship between the habit of writing and the habit of art. Then stop by Flavorwire and see a sampling of her cartoons from Flannery O'Conner, The Cartoons.