From his 1982 Paris Review interview:
That’s what I try to do — write sentences that won’t be like sand castles. I’ve gotten to the point where I seem to recognize a good sentence when I’ve written it on the typewriter. Often it’s surrounded by junk. So I’m extremely careful. If a good sentence occurs in an otherwise boring paragraph, I cut it out, rubber-cement it to a sheet of typewriter paper, and put it in a folder. It’s just like catching a fish in a creek. I pull out a sentence and slip a line through the gills and put it on a chain and am very careful not to mislay it. Sometimes I try that sentence in ten different places until finally it finds the place where it will stay — where the surrounding sentences attach themselves to it and it becomes part of them. In the end what I write is almost entirely made up of those sentences, which is why what I write now is so short. They come one by one, and sometimes in dubious company.I’ve just begun reading Maxwell’s So Long, See You Tomorrow. No dubious company to be found.