Here's something that I never knew about Vonnegut's writing tips, until I started doing some research. He had a corollary:
The greatest American short story writer of my generation was Flannery O’Connor (1925-1964). She broke practically every one of my rules but the first. Great writers tend to do that.
And here’s the most important thing to Vonnegut’s rules. Great writers don’t need rules—they just write. If, in the end, the reader enjoys and values the work, nothing else matters.
My goal in writing: Forget about the rules...just write the best possible thing I can ever write.