Below is the first of Janet Fitch’s 10 Writing Tips That Can Help Almost Anyone: it’s from her website http://janetfitchwrites.wordpress.com/ and I encourage you to go and look at it. Right now!
1. Write the sentence, not just the story
Long ago I got a rejection from the editor of the Santa Monica Review, Jim Krusoe. It said: “Good enough story, but what’s unique about your sentences?” That was the best advice I ever got. Learn to look at your sentences, play with them, make sure there’s music, lots of edges and corners to the sounds. Read your work aloud. Read poetry aloud and try to heighten in every way your sensitivity to the sound and rhythm and shape of sentences. The music of words. I like Dylan Thomas best for this–the Ballad of the Long-Legged Bait. I also like Sexton, Eliot, and Brodsky for the poets and Durrell and Les Plesko for prose. A terrific exercise is to take a paragraph of someone’s writing who has a really strong style, and using their structure, substitute your own words for theirs, and see how they achieved their effects.