Back in 1982, advertising copywriter David Ogilvy sent out a memo on how to write.
As he noted, the better you write, the higher you will go in Ogilvy & Mather (the advertising agency he founded).
While these hints are great for advertising copywriters, they are also generally valuable to book authors as well (except, of course, tip #5: Never write more than two pages on any subject). Tip #5 would be hard to follow as a book author. It’s hard to bind two pages into a stand-alone book.