It is not good--and indeed it hinders the creative work of the mind--if the intellect examines too closely the ideas pouring in, as it were, at the gates . . .. In the case of a creative mind, it seems to me, the intellect has withdrawn its watchers from the gates, and the ideas rush in pell-mell, and only then does it review and inspect the multitude.
Johann von Schiller
Remember that the goals are to gather as much material as you can--however tangential it may sometimes seem--and to let your mind play over it.
See the "Getting Material" section for specific strategies.
My favorite incubation story comes from the time when I invited Jack Smith, a columnist for the Los Angeles Times, to talk to a first-year writing class I was teaching at UCLA. Smith wrote a daily column about Los Angeles; these columns were so popular that a number of published collections of them had appeared, bearing titles such as The Big Orange.
The students asked Smith how he was able to write a column every day. How could he keep producing quality material when he had a constant deadline hanging over his head?
Smith smiled as he stood at the front of the room. He said that the only way he could maintain the pace was by writing while he slept--literally. His writing process went like this: before he went to sleep, he would get clear in his mind what his topic and theme were going to be for the next day's column. Then, he would commission his subconscious to do the work of filling the column in.
The next morning, he said, he would wake up and it would be as if he were a child coming downstairs on Christmas morning and finding the tree fully ornamented and the presents spread beneath. The column would be complete in his mind.