Oliver Kamm in The Times of London:
Almost at random, I pick from my shelves the celebrated American manuals The Elements of Style by William Strunk and EB White and On Writing Well by William Zinsser, along with On Writing by the bestselling author Stephen King and Do I Make Myself Clear? by the former newspaper editor Sir Harold Evans. All say the same thing: omit needless words, avoid the passive voice, and cut out adjectives and adverbs.
The hollowness of this advice is inadvertently demonstrated by the authors themselves, for in giving it (and apparently without realising it) they extensively employ the passive voice along with adjectives and adverbs. “Adverbs, like the passive voice, seem to have been created with the timid writer in mind,” writes King (the words I’ve italicised are a passive clause). Most adjectives are “unnecessary”, declares Zinsser, using the adjective unnecessary. Adjectives are “seductive”, warns Evans, using the adjective seductive. “With adverbs,” continues King, “the writer usually tells us he or she is afraid he/she isn’t expressing himself/herself clearly, that he or she is not getting the point or the picture across” — using the adverbs usually, clearly and across.
See what I mean? Even famous writers aren’t necessarily able to explain good writing or even understand grammatical categories.
More here.