I've always liked Stephen King. One piece of advice, first said by William Strunk and reflected here, has stayed with me: omit needless words. Now I take out all unnecessary adverbs and adjectives, which are most of them. I like to think my writing has improved. A quote cited in his book, On Writing, was also a revelation:

"I made this letter longer than usual because I lack the time to make it short." -- Blaise Pascal

My friend and I used to laugh at this quote because we thought it wasn't true. Now we laugh because we know it is.